Britain's most senior police chief has called for new laws to combat terrorist conspiracies, saying the UK is being targeted by "al-Qaeda affiliates".
Sir Ian Blair said questions needed to be asked about the legal system
Metropolitan Police Commissioner Sir Ian Blair also voiced support for ID cards, on BBC's Breakfast With Frost.
Sir Ian cited the case of ricin plotter Kamel Bourgass who had used aliases.
But campaign group Liberty said Sir Ian should be politically "independent" and his comments were "dangerous" as others had been cleared in the Bourgass case.
Bourgass was found guilty of murdering Special Branch Det Con Stephen Oake in a Manchester flat in January 2003, and on Wednesday received a further 17 years for conspiring to cause a public nuisance after police discovered what they believed was an al-Qaeda ricin poison plot.
Bourgass, from Algeria, was in Britain illegally when he killed Det Con Oake.
Eight other men accused of playing a part in a suspected poison plot were cleared of any involvement.
Sir Ian stressed it was important to recognise that Bourgass was only "one individual".
He said 99.9% of Muslims and 99.9% of Asians were "law-abiding people and we've got to support them in that and understand the difference".
He added legislation around "acts preparatory to terrorism" was needed to deal with cases such as those involving Bourgass, as al-Qaeda operates using "very loose-knit conspiracies".
He said: "There's real clarity now that al-Qaeda affiliates are targeting Britain."
Asked whether ID cards should be introduced after the election, he said: "I think there has to be further consideration of that.
Kamel Bourgass plotted to release ricin poison in London
"I wasn't particularly keen on ID cards until recently - until I began to understand the way in which identity theft is carried out.
"There are no more printing presses in basements. The documents that are being produced are exactly identical to the real documents, they're just unauthorised," he said.
"And so we have to go to a place where we do know who people are. We now have the technology, I think through iris recognition, to go to that and I think that would be very helpful."
He said the problem with people such as Bourgass was that they were unknown to authorities.
Labour are in favour of an ID card scheme, whereas the Liberal Democrats are opposed and the Conservatives promise to review the idea, if elected.
Labour's election co-ordinator, Alan Milburn, said that if returned to power, the party would immediately re-introduce the Identity Cards Bill, "which we consider to be a major priority".
BBC political correspondent Shaun Ley said Sir Ian was "pushing at an open door" on the issue of new laws to punish terrorist conspirators.
He said the Tories had stated they would introduce the law if elected. The Lib Dems believe a consensus could be found after the election, he said.
However, comments on the ID card scheme were "highly political" and "very potentially controversial", he said.
Shami Chakrabarti, director of civil rights group Liberty, said the case for compulsory ID cards had not been made.
She added: "I think it is very important that the Metropolitan Police commissioner respects the law and stays independent of politics.
"It's dangerous to cast aspersions on people who have been found not guilty by a court.
"I think he should be a little bit more judicious about the timing of some of these comments.
"It is already very, very hard for acquitted people who are also asylum seekers not to be completely demonised in the media."