Government plans to increase the terror detention limit to 42 days will be destroyed by a defeat in the Lords, a leading Conservative has said.
Ex-shadow home secretary David Davis told BBC One's Andrew Marr Show he expected peers to reject the proposals by a "huge majority" on Monday.
Even most Labour peers would not support the plans, he predicted.
The government argues that extending the detention limit is necessary to foil increasingly complex plots.
Mr Davis, who resigned as an MP to force a by-election over the government's record on civil liberties, said: "I think it will be dead."
Narrow Commons vote
The government's measure, increasing the pre-charge custody time limit for terror suspects from 28 to 42 days, passed through the House of Commons by nine votes in June.
It is opposed by the Conservatives and the Liberal Democrats.
The government thought by having 42 days and us opposing it they would make us look weak and them look strong
Peers will vote on Monday and Mr Davis said: "I think it will be thrown out by a huge majority."
He added that the extension, contained in the Counter-Terrorism Bill, no longer had support from the public - and the government would not have the political will to force it through using the Parliament Act to overrule the House of Lords.
Mr Davis said: "It was something that was profitable for the government - they thought by having 42 days and us opposing it they would make us look weak and them look strong.
"That was when 70% supported it; now it's about 30% supporting the government."
He added: "Their own party probably won't support them in the Parliament Act, so I think it's probably over."
Mr Davis shocked Westminster by standing down as MP for Haltemprice and Howden in protest after the Commons passed the measure.
He was re-elected after a campaign designed to highlight what he described as the "erosion" of civil liberties under Labour.
The government argues there may be occasions when a suspect has to be held for longer than 28 days before a charge can be brought, because of the increasing complexity and scale of the terrorist threat.
Mr Davis, who visited Afghanistan last week, also told the Andrew Marr show that Britain was facing a "disaster in the longer run" in Afghanistan unless it changed its strategy.
Ordinary Afghans thought Nato-led forces were losing and did not see them as liberators, he said.
His comments come after a major battle on the outskirts of Lashkar Gar, capital of Helmand province, in which dozens of Taleban militants were reportedly killed.
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