Gordon Brown was facing a two-month battle last night to avoid defeat over his attempt to gain the power to detain terror suspects without charge for 42 days.

As the Prime Minister attempted to steady Labour’s nerves about its electoral prospects and an economic downturn at a meeting of the parliamentary party last night, one backbencher predicted that he would be forced to turn to the Rev Ian Paisley and his nine Democratic Unionists to get the detention proposals through.

Government sources admitted yesterday that they faced defeat as things stood, although one member of the Government told The Times: “I would say there is still a way to go, but we are reasonably optimistic.”

But John Grogan, MP for Selby and one of the opponents of the plan, said: “It is fairly solid with up to 40 Labour rebels. The Government’s only hope of getting it through is doing some kind of deal with the DUP. This has been endlessly debated over the past few years and people are quite clear where they stand.”

Although some Labour MPs who opposed the 42-day limit will speak out today, as the Counter-Terrorism Bill has its second reading in the Commons, others who are unconvinced are likely to keep their counsel until the critical vote on the proposals, which is expected in mid-May.

The Government is signalling that it is prepared to make concessions in two areas in order to win further support. On the key issue of how quickly Parliament must vote to approve the extended detention powers, ministers are willing to bring the deadline forward to as little as a week.

The second concession is likely to be over what could trigger holding suspects for up to 42 days. The Government is prepared to go further in setting out in the Bill what constitutes an emergency.

Neither the Conservatives nor the Liberal Democrats have tabled reasoned amendments opposing the Bill’s second reading, meaning that there may not even be a vote unless some diehard Labour rebels force one.

One government source said: “There may be some abstentions and rebellions but not very many and those people who are reserving their positions will be biding their time.”

Conservative MPs are on a one-line whip for today’s debate, the lowest status, and if forced to vote those present will probably back the Bill rather than be seen to oppose counter-terrorism measures in the run-up to the local elections next month.

A total of 51 Labour MPs rebelled when Tony Blair tried to extend the maximum period of pre-trial detention without charge from 14 to 90 days in November 2005, triggering his first Commons defeat as Prime Minister as MPs instead backed a 28-day limit.

Then the Democratic Unionists voted against the plan, with only one Tory MP, Sir Peter Tapsell, and the sole Ulster Unionist, Lady Sylvia Hernon, in favour as the Government’s majority fell to 33 in one vote and 31 in another. A handful of other Tories abstained or opposed the shorter 28-day limit.

This time the Government has opted for a softly-softly approach with Jacqui Smith, the Home Secretary, holding one-to-one meetings with potential rebels to explain the plans. But she faces competition from counter-briefings by Shami Chakrabarti, the director of Liberty, who appears to have the upper hand.

Some backbenchers who supported Mr Blair’s plan for a 90-day limit have switched to the rebel camp, including Andrew Dismore and Frank Cook, arguing that 28 days are enough.

Two of the rebels from the 2005 votes are now members of the Government who will have to support the plan or quit: Joan Ruddock, the Environment Minister, and Sadiq Khan, a whip. A third, Mark Lazarowicz, is now a ministerial aide who is also required to support the Government or resign. In addition to the plan to extend the maximum period of pre-charge detention to 42 days, smaller numbers of Labour backbenchers also have concerns about proposals to allow post-charge questioning of terror suspects and to admit intercept evidence in court for terror trials.

At their weekly meeting last night, some backbenchers also voiced concern to Mr Brown about the Government’s handling of post office closures and the Budget, especially its abolition of the 10p starting rate for income tax, saying they were facing criticism in their constituencies for both.

Mr Brown told them Labour must show it was on the side of voters on key issues, echoing a criticism of the junior minister Ivan Lewis, who suggested the Government was out of touch after 11 years in power.

Ministers are braced for poor results in the local and London elections, including the possible loss of the London mayoralty to the Conservatives, and MPs are downbeat about polls showing Labour trailing heavily.

Times Recommends

• Tree stump 'shows image of Virgin Mary'
• BBC drops Strictly judge for younger model
• Trafalgar Square 'reduced to a spectacle'