Britain's former spy chief Baroness Manningham-Buller has told the House of Lords she is opposed to Government plans for 42-day pre-charge detention.

Lady Manningham-Buller, who served as director general of M15, said the proposals were not "workable".

In her maiden speech to the House of Lords, she said: "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 judgments honestly reached by others and I respect these views.

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

She was speaking as the debate over the controversial plans for terror suspects switched to the House of Lords.

The Government's proposals to extend the maximum time suspected terrorists can be held before being charged are likely to be soundly defeated.

Peers will not vote on the controversial plans until a later date, but former ministers Lord Goldsmith and Lord Falconer are expected to savage them.

The 42-day proposal is almost certain to be stripped out of the Counter-Terrorism Bill when the details of the legislation are considered by peers, possibly after the summer recess.

The Counter-Terrorism Bill is to be considered by peers following the Government's narrow victory last month in the Commons, where Gordon Brown narrowly averted a humiliating defeat by just nine votes.

The support of the nine Democratic Unionist Party MPs was crucial after 36 Labour backbenchers rebelled.

Thursday will see the Haltemprice and Howden by-election, which was triggered by Conservative front bencher David Davis's resignation after the vote.

The then shadow home secretary said he wanted to stand for re-election on a civil liberties platform and neither Labour nor the Liberal Democrats have entered candidates for the contest.

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