MPs have been evacuated from the House of Commons after a condom filled with coloured flour was thrown at Prime Minister Tony Blair.
Fathers 4 Justice claimed responsibility for the incident, which cut short Prime Minister's question time.
Labour peer Baroness Golding said in a statement that the two protesters were guests of hers.
Mark Oaten, the Liberal Democrats home affairs spokesman, called for an urgent review of security arrangements.
Send us your reaction to the incident. Is security in the House of Commons adequate?
This debate is now closed. Read your comments below.
The following comments reflect the balance of opinion we have received so far.
This is yet another example of how far people in this country feel they have to go to register their displeasure at the current government. When will the Labour Party realise that everything is not sweetness and light and that there is a lot of ill feeling against what has been done to this country by the current government.
All visitors should be screened from the chamber, or excluded altogether. Their presence doesn't contribute to a better democratic process in any way, after all, the process is on TV. If we can't protect those whom we elect to run our country we don't deserve democracy.
Paul Bell, Grimsby, NE Lincs
Why do they get so much spent on them when we've not so much as had a leaflet telling us what to do in event of a biological or chemical attack?
Ian, Arbroath, Scotland
While they're at it, they should close it to MPs too, after all, they don't exactly do anything constructive do they?
John, Battersea, England
To the people that think these men should not have access to their children "after Pulling a stunt like this" You should consider how you would feel, if for example you'd not seen your son or daughter for four or five years. Its desperately sad, and sometimes desperate measures need to be taken. So to all the do-gooders out there, speak to someone who knows a little about it before making off the cuff remarks.
I demand that Justice be done! Where on earth were the eggs and rotten tomatoes!?
Flour Power, Man?
If this had been suspicious powder thrown around a public event, I'm sure we would have been locked in until the powder was identified. How dare the MPs run the risk of spreading something around? One of them was mixing with TV crews telling them how he had "no idea" what the powder was. Talk about leading by example.
Owain, Slough, UK
Lets have some perspective. It was purple flour and not the gunpowder plot. Government has always been a risky business - ask King Charles 1st - he lost his head over it! The commons was established for the common people to have a say in the running of their country - let us not allow the new elite of politicians keep us out for fear that they might find out how we really feel about their policies. Yes there needs to be security, but lets not over-react..
Observing democracy at first hand is a very different experience to watching it on the television. Even if we have to increase security, we should never forbid MPs from inviting guests to the Chamber.
Paul Evans, Exeter, UK
Surely the last thing to have done under the circumstances was to evacuate the premises. If the substance had been a chemical agent then obviously all who had been in contact should have remained secured inside to await the detox squad. Isn't that the standard procedure that half of London was brought to a standstill to test not so many moons ago?
Alan Schofield, Limassol, Cyprus
In the 18th Century unpopular politicians were pelted with rubbish and dead cats whenever they appeared in public. Today they're cocooned in security. We are all at risk from the determined terrorist. If Mr Blair is more at risk isn't this an occupational hazard?
T P Gibbon, London
It is right that people should maintain an interest in politics but we must never forget that we are, every day, being targeted by terrorists. Security checks and ID cards did not prevent the 911 or Madrid attacks and to assume that the commons is immune to terrorists is hopelessly naive.
Peter Martin, UK
Supposing the Prime Minister, his Cabinet and all MPs had been killed who would take power?
Edmund Montgomery, Derby, England
Since the Commons is televised I see no reason for non-essential people to be in the building anyway.
David Meagor, Plymouth
Would you let someone who does an outrageous stunt like this have access to your child?
Are all these people saying "We need better security! Our politicians must be protected!" the same people who said "We must not change, or the terrorists will have won!"? I think we should be told.
James Cort, Bristol
Of course the Commons should stay open to visitors. It's a right symbolic of open government. Otherwise Parliament might as well be manufactured in a studio somewhere near Milton Keynes.
Richard Kemp, Cambridge, UK
I have visited both the US Senate and the House of representatives. This was late last year, well after 9-11 but they felt no need for bullet-proof screens or the like. Instead they did thorough screening of visitors, which everyone was perfectly prepared to accept. The "flour bombers" were in a "VIP" area and had apparently not been subject to proper searching - there's the problem, a quaint notion that because that area is reserved for invited guests they represent less of a threat. Forget your expensive bullet-proof shields -screen and search visitors properly.
Bill D., London
Hmm... it raised the profile of a worthy cause, safely indicated a dangerous loophole in Commons security and above all was pretty damned funny. I don't see the problem.
Absolutely not. Our civil liberties are being eroded on a daily basis because of fears of terrorism. States around the world are using September 11th and other attacks to hike security up further and further. The Commons must remain open to the public. I do not believe that a terrorist would have got to that open area with anthrax or another substance as the papers are reporting. Vet people better, yes, but do not take away the opportunity to go to parliament and take an interest in politics.
I think one very important point is being overlooked. Why were the MPs allowed to leave the chamber so quickly? It's galling to think that if it was anything nasty, then our esteemed elected representatives could have been eagerly spreading a biological problem around London 20 minutes later. Seeing John Reid on TV yesterday saying "how quickly we got out of there" just made me heave.
Jamie, Herts, UK
What sort of democratic institution has selected 'privileged' seats for friends and family of members of government.
Tony, Petersfield UK
I think the gravity of the incident is only just sinking in. This could have wiped out not only the Government, but the whole of our political elite on all sides of the Chamber. I bet terrorists are kicking themselves that they did not enter the raffle.
Roger Morgan Freedlan, Whitwick, UK
I think we have to look at this from a different angle. What made them so desperate? Why aren't these people who have a very good case being heard? Are there too many career politicians who are afraid to take on such an issue? There seems to be no debate for ordinary people, just 'hot topics' like ID cards and other ways to spend our taxes. These fathers are having their human rights abused. What they did was wrong, but why they did it was right.
Chris, Leiden, NL
They behave like this, yet they're still surprised that a court decided they weren't fit to look after their kids? Incredible.
Andrew, London, UK
I cannot imagine a more emotive issue for fathers than to be denied access to their children while some stranger has 24 hour access. The whole issue needs to be looked into and some hope offered to these desperate men.
Anthony, Birmingham, UK
Amazing how all security measures have a "back door". It doesn't matter how many searches, X-ray machines, armed police or security screens are put in place, they are useless if they can all be bypassed by one person vouching for another that they are "alright".
Totally unacceptable, you DO NOT raise your hand against your elected leader no matter what. What kind of message are you sending to the rest of the world?
Dalley Nigli, Romford
I'm all for protest and causing a stir to raise awareness of issues and effectuate social change, but throwing condoms in the House of Commons? Certainly there are more effective methods to bring publicity to your cause. What are have we become, children in the lunch room at school having a food fight? This seriously lowers the bar for creative protest.
Fantastic shot! I am very impressed with the attacker's aim! Is he a cricketer?
Lisa Davis, Detroit, USA
Your reporter said "The prime minister appeared unsure of what was happening to him before he was ushered slowly, almost bemused, from the chamber." - Nothing new there then.
Only when you have come home from work one day, to find your wife has left and taken the children, and you have no right to see your own children, ever again, can you possibly understand what drives decent, respectable fathers to do what these two did today.
Ray Barry, Wolverhampton, UK
What an utterly moronic thing these silly protestors have done. I hope the full weight of the law is brought to bear upon both of them and that the peer who signed them into the House is thrown out of the Lords for being party to such irresponsible behaviour.
I haven't seen my 2 daughters for 8 months now. Anything that raises the profile of the problems of the family court is a good thing. Well Done!
Steve Mayall, Folkestone
These Fathers 4 Justice have been a pain in the backside for years now, and this is one eye-rolling exhibitionist display too far. There are more appropriate ways to solve your problems than this.
Alex Nolan, Ormskirk, UK
Another protest that illustrates the gaping holes in the security arrangements surrounding the House of Commons. People in this country seem to be in a strange denial about the seriousness of the terror threat this country faces.
For the ones involved in the stunt, it only adds fuel to their partners for not allowing access to their children. Also brings the wrong kind of attention to the kids in school.
Brian Aldridge, UK
As a taxpayer I object to £600,000 being wasted on a temporary screen that is supposed to prevent this sort of thing. This is typical of politicians; spend a lot of money to implement an ineffective solution. No doubt even more public money will be wasted to try to plug this insecure security device.
Duncan, Salisbury, UK
Before this attack I had quite a lot of respect for Fathers 4 Justice, but this is one protest too far. In this country we have a right to peaceful protest but this childish act could end up jeopardising those rights. Fathers 4 Justice should swiftly distance themselves from this protest or they will risk losing a great deal of support, they have already lost mine.
Ben Archell, Bromley, Kent
I think we are completely over-reacting. What is needed in the Commons is a proper search procedure, just as you would have before going on an aircraft. If it's good enough for 350 people in the sky, it's good enough for our MPs. But a clear 'NO!' to the glass screen!!!
Nick Odoni, Southampton, Hants
Security at the House of Commons is clearly all wrong - there are not nearly enough incidences of cake ingredients being thrown at the government benches!
It was a desperate reaction to a desperate situation for far too many of us. Fathers are being ignored by the courts, the social services, the entire system. Perhaps when Tony Blair looks at his jacket again, he will remember that a problem exists - one that far too many people in the system have forgotten about.
John G., Antrim, N. Ireland
This incident just hastens the day when even legitimate protest may be curtailed. These people represent nobody but themselves, but may succeed in affecting the rights of the rest of us.
I take it from all the people leaving negative comments regarding the actions of Fathers 4 Justice, that they are or never have been denied access to their children. These people are desperate to see THEIR children and are being denied rights to do so! What would you recommend they do?? They have gone to courts, run up massive legal bills to win rights to see their children, only for their ex-partners to STILL refuse access. Then they go to court again at their own expense, only for the continuous malicious circle to continue!! Good on them and keep up the fight lads!
Simon Hulse, Worcester
Oh good, so MP's get more security whilst we have to suffer the risks of their decisions without screen, concrete barriers and hundreds of security officers. Any one of us could be a target, at any time and anywhere. I think MP's get enough protection already.
The protest on The London Eye made no difference and no doubt, neither will this. This government does not take any notice of public opinion. Only problem there is that neither did the Tories!! What are we to do?
Linda Sloan, England
Thank God they didn't have anthrax powder in those "bombs". Only in Britain could we spend 600 grand on a security screen and leave a big hole in it for certain "VIPs"!
Matthew Knowles, Loughton, UK
I have to hand it to Fathers 4 Justice, they know how to carry out high profile stunts to reach as wide an audience as possible. And a good thing too - I hope these protests, however inappropriate they may be in some people's eyes, attract enough attention to their cause that it is properly addressed. I fully support their actions so far.
Jon Charman, Horndean, England
To those who think this is just all a laugh - remember that this shows that terrorists could, if they wanted to, carry out an attack with something more dangerous than purple flour. Remember they were invited by a peer, and this Government did decide to give former members of the IRA offices in the Commons. Who would they invite?
Graham, Andover, England
Its a pity this will close off government even more. Why should they spend hundreds of thousands erecting a barrier between them and the public they are supposed to serve? If they don't like the security risk of being a politician then how about not being a politician !
Martin Mace, Cambridge, England
A lucky warning! The purple powder could have easily been something more sinister. It is surprising that security can be so lax.
Fathers 4 Justice are giving us a master class into how to take a good cause and make it extremely unpopular. Blocking traffic and now abusing the open-access policies of the House of Commons has convinced me that these fathers do not deserve access to their kids - they should be locked up for their own safety and the public's convenience. It will be a real shame if the House of Commons is closed to the public after this childish attack.
Security is clearly not tight enough, which is worrying given that it was supposed to have been increased recently. However, the public gallery must stay open. Seeing parliament in operation first hand is something that all of us should be able to do.
David Patrick, Reading, UK
Parliament has clung to old-fashioned ideas about public access, forgetting that in a multimedia age, people have a far greater insight into the running of the country than ever before. Security should be tightened and brought up to date with the realities of living in a modern industrial society.
Bob Hockney, London, UK
All this sort of action achieves is the raising of more barriers between us and our elected representatives. We may have legitimate grievances against our leaders but this action is just violence.
This incident demonstrates precisely why some fathers are not responsible enough to have access to children. What kind of example is this to set?
I'm sure the Government will see this as justification to spend even more on their own security, whilst the rest of us continue to take our chances on the tube to our high rises in the City.
Neil, London, UK
This was not a serious security risk - the guests to the House of Commons were known to Baroness Golding. Would a member of the House of Lords welcome a security risk into the Commons? I think not. So, what does this demonstrate? If you invite people into the Commons, they might be involved in a small-scale dissent. Let's not panic on this one, it's trivial.
Andrew K, Durham, UK
If only the protesters' aim had been better, though how they missed hitting someone with an ego the size of Blair's is beyond me!