Former head of MI5 says 42-day detention plan is 'unworkable'

Plans to hold terror suspects for up to 42 days are neither practical or principled, the former head of MI5 warned yesterday.

Baroness Eliza Manningham-Buller, who stood down as the director general of Britain's domestic intelligence agency last year, took the highly unusual step of using her maiden speech in the House of Lords to denounce the plans. It was the first time she had spoken on the subject.

"I don't see on a practical basis, as well as a principled one, that these proposals are in any way workable," she told peers.

The comments by Lady Manningham-Buller, an anti-terrorism specialist who led MI5 during the London Tube bombings three years ago, represent a serious blow to Gordon Brown's anti-terror laws, which were forced through the Commons on the votes of Democratic Unionists (DUP) last month after a major rebellion by Labour MPs.

She told peers: "I have weighed up the balance between the right to life – the most important civil liberty – the fact that there is no such thing as complete security, and the importance of our hard-won civil liberties. Therefore, on a matter of principle, I cannot support 42 days' pre-charge detention. I do understand different views and that there are judgements honestly reached by others, and I respect these views."

Peers are expected to vote overwhelmingly to defeat plans to extend detention without trial when the anti-terror Bill faces detailed scrutiny in the autumn, and will trigger a damaging new round of trench warfare for Mr Brown in the Commons.

Yesterday, a string of eminent figures in the Lords vented their anger at the proposals, attacking them as an affront to civil liberties and a recruiting sergeant for extremists.

Lord Falconer, the former lord chancellor and one of Tony Blair's closest allies, said: "I'm absolutely clear that there is no advantage to fighting terrorism that will be gained by extending pre-charge detention to 42 days."

He criticised the Government for relying on the DUP to get the Bill through the Commons, adding: "We in this country determine whether people should be detained on the basis of a judge's view. I find it worrying that someone could be detained in prison on the basis of a deal done with another political party."

Lord Goldsmith, the former attorney general, also condemned the proposals, telling peers that "you cannot keep somebody for as long as it takes." He added: "I dealt with the plots which we believed were being uncovered in the summer of 2006.

"I flew back from my holiday. I stayed with the prosecutors and got detailed briefings through that period. I was anxiously considering and wanting to know whether a longer time was necessary. It wasn't. "I asked the prosecutors, 'If you had had longer than 28 days, would you have used it?' 'No', they said.

"I cannot support this. I believe that detention without charge for a long period would undermine fundamental freedoms on which this country is based, of which this country should be proud, of which I will say my party ought to be proud. I will not undermine them in this way."

But Lord West of Spithead, the Security minister, insisted the new powers were needed. He said: "The question we all have to face is whether there is a potential need for more than 28 days. I have looked at this in depth and I believe there is. It is better for us to legislate on a precautionary basis than find ourselves scrambling for emergency legislation in the heat of a serious operation."