Tony Blair warned today that there are "several hundred" individuals in Britain who are planning terrorist attacks.

The Prime Minister said that he would be negligent if he ignored the advice of the security services and police, who had told him that increased powers were needed to combat the threat.

Mr Blair's comments, during an interview on BBC Radio 4's Woman's Hour, will increase the pressure on rebellious Labour backbenchers to support the Government's controversial Prevention of Terrorism Bill in the House of Commons tonight.

Mr Blair also implied that the Government would not be watering down the legislation for control orders in an attempt to placate MPs opposed to the measures being introduced in the Bill.

"I can't make a concession on the basic principle, because that would be to ignore the advice I'm being given," Mr Blair told listeners.

"What they say is you have got to give us powers in between mere surveillance of these people - there are several hundred of them in this country who we believe are engaged in plotting or trying to commit terrorist acts - you have got to give us power in between just surveying them and being sure enough to prosecute them beyond reasonable doubt.

"There are people out there who are determined to destroy our way of life and there is no point in us being naive about it.''

His comments came as Saajid Badat, a 25-year-old Briton from Gloucester, this morning admitted involvement in a plot to blow up an aircraft. He pleaded guilty at the Old Bailey in London to the charge of conspiring with shoebomber Richard Reid and a Belgian terror controller.

Mr Blair defended his draconian proposals to allow politicians to lock people up on secret evidence on the grounds that they would only be used in the "most limited circumstances". He insisted however that the powers were genuinely necessary to protect the UK.

"We don't get to house arrest under the proposals we have put together unless the security services actually advise in respect of any one particular person that it is vital that we do it," he said.

Civil liberties were important to him, the Prime Minister said, having been a lawyer working in the area and introducing the Human Rights Act to Britain.

Michael Howard told BBC Radio 4's Today programme that he hoped a compromise could be reached.

"It is something which we ought to deal with by way of consensus. I have made that clear from the word go.

"We do face a terrorist threat. We have to take action to deal with that terrorist threat. But it was rushing a Bill through Parliament which got us into the mess we are in today, and now the Government is doing exactly the same thing again, rushing the Bill through the House of Commons in two days flat.

"We have offered them a number of alternative ways in which they can proceed. I hope they will listen.''

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