By Jane Hughes
BBC News health correspondent
John Reed was injured on duty
Ambulance workers around England are coming under attack on a regular basis, according to the Liberal Democrats.
They have released figures showing more than 7,000 homes are "red flagged" as too dangerous for ambulance workers to go into without back-up.
Ambulance workers union, Unison, says the policy of "red flagging" is presenting crews with tough moral dilemmas.
They are left weighing their own safety against the well-being of the patient.
Ambulance services commonly use dispatching systems which create an "alert" for any address that poses a risk to crews.
These include addresses where ambulance staff have experienced violence, aggression or sexual threats, or have encountered dangerous dogs.
They may also be warned if a patient has alcohol-related or mental health problems.
Attacked by patient
John Reed, a paramedic based in east London, knows how it feels to be at the receiving end of violence.
A couple of months ago, he was attacked by a patient who appeared to have passed out.
He was kicked in the ribs and knocked unconscious.
He says the back-up ambulance that was sent out for the patient ended up taking him to hospital instead.
"It saddens me," he says. "It's a shame that people we go to treat are going around attacking us when all we want to do is help them."
Steve Elliker, head of security and safety for West Midlands Ambulance Service, has seen the number of attacks increase steadily.
In the year to last April, 28 people were convicted of violence against ambulance staff in the region.
In the first ten months of this year, there've already been 34 prosecutions.
Mr Eliker makes sure staff are trained to deal with aggression and defuse tense situations.
If they are called out to addresses which are "red flagged", they are advised to wait for back-up, either from another ambulance crew or from police.
They also have the final say over when to begin treatment.
But does that mean patients in life threatening situations may be left waiting for help?
Mr Elliker acknowledges that it is a possibility.
He said: "They have to make a judgement call at the end of the day.
"Paramedics are only as good as the skills they can deliver, and if there's any fear they can't deliver those skills because of the threat of violence they have an automatic right to withdraw."
He adds, however, that it very rarely comes to that.
The Liberal Democrats say some parts of the country have hundreds of addresses where caution is advised.
In the North West, 3,071 addresses are considered risky.
Health spokesman, Norman Lamb, is calling for greater protection for ambulance staff, including body armour, currently only available to them in some parts of the country.
He said: "Here we have members of a caring profession, providing support for people at a time of need, and this level of violence really isn't acceptable."
The ambulance workers union Unison believes staff are being left with moral dilemmas.
Karen Jennings, the union's head of health, said: "I think there are serious questions to ask about whether ambulance crews should sit outside if somebody inside is having a heart attack."
"Having said that, if that household has a history of attacking people when they go in, then it doesn't do anybody any good if they were just to rush in and put themselves at risk."