British troops will not be pulled out of Iraq, the prime minister has insisted.

Speaking to the BBC on Sunday, Tony Blair said that their key role in assisting security and reconstruction in the country should continue.

His comments came amid continued fears for the safety of Kenneth Bigley, the hostage being held in Iraq by Islamic militants.

Blair said that the government was doing what it could to secure his release, but insisted that the government would not advise contractors or aid workers to leave the country.

"It is important that the reconstruction work in Iraq goes on, because what's happening in Iraq at the moment is very clear," he told Breakfast with Frost.

"There are aid workers, construction workers, non-governmental organisations, the presence of troops there, trying to help Iraqis make their country better, to help them make it a democracy.

"The purpose of these terrorists is to stop it. Of course it's very difficult. However, the question is what is our response to this situation.

"When I hear people say because of the difficulties, we should pull our troops out, my response is that would be to surrender to the terrorists. That's not what we should do.

"These people who are holding hostages in Iraq, these people who are conducting many of the killings of totally innocent people, are not actually Iraqis.

"They are people from outside. They are people linked to this global terrorism that we live in the midst of today, who want to use Iraq as a battleground.

"What we have got to do is to be in there and to beat them and to work with the Iraqi people in order to build up their own capabilities but also make sure that we stay there until the job is done."

Blair also expressed his feelings on seeing Kenneth Bigley's videotaped plea for assistance.

"My first reaction is the reaction of anyone, which is real sympathy for him, anger at how he is being held by those people and an earnest hope that, despite all the difficulties, we can do something," he said.

"But I just don't know if we are able to or not. As I have said throughout, there is no point raising false hopes because of the nature of the people we are dealing with."

He added: "Insofar as it is possible to do things, we are doing them. I won't go into the details of that for obvious reasons.

"But we are doing everything we properly and legitimately can and I think and hope people understand that."