Downing Street last night stood firm on the issue of 42 days' pre-charge detention for terror suspects but hinted it might give ground to the rebels over the related issues of parliamentary and judicial oversight of terror cases to stave off a damaging Commons defeat.

With June 10 or 11 pencilled in for the crunch Westminster vote on the UK Government's flagship Counter Terrorism Bill, the persuasive charms of Geoff Hoon, the Chief Whip, and Jacqui Smith, the Home Secretary, are being employed on potential rebels who could inflict another embarrassing blow on an already beleaguered Gordon Brown seeking to regain the political initiative.

The Prime Minister's spokesman, asked if the UK Government was preparing the ground for a tactical retreat, insisted: "There can be no question of any compromise on 42 days."

The possible deal to dissuade back benchers from rebelling is thought could include: first, ministers declaring an "exceptional need" to use the proposed power of detaining someone up to six weeks, including such circumstances as the discovery of multiple terror plots; secondly, authorisation by Westminster brought down from taking 30 days to just seven; and, thirdly, a review by a judge of the parliamentary use of such a power.

One UK Government insider said: "The rebels are not going to be fobbed off with small stuff, but once you get to the detail the differences between the two sides are bridgeable."

Yesterday, rebel Labour MPs tabled their amendment, which would block the PM's bid to extend pre-charge detention to 42 days. One, David Winnick, the MP for Walsall North said: "There is a reasonable chance the government will be defeated but I do accept it will do everything in its power to try to persuade some of my colleagues to agree on the basis of various concessions."

While the police are backing the UK Government, other forces are set against it, including Lord Goldsmith, the former Attorney General, Sir Ken Macdonald, the Director of Public Prosecutions, and the Conservatives, LibDems and Nationalists. On Wednesday, Westminster's Joint Committee on Human Rights, made up of MPs and peers, said an extended detention limit was "unnecessary".

Civil rights campaigners also oppose Mr Brown's plan. Last night, Shami Chakrabarti from Liberty said: "Parliamentarians of all parties have united in opposition to this dangerous and counter-productive measure. In the face of all evidence, ministers talk of exceptional powers then deliver a bill that would allow six weeks' detention to become almost the norm. Now is the time to put principle over politics. We urge the government to think again."

However, Mr Brown received support from an unexpected quarter - Frank Field, the Birkenhead MP who led the 10p tax rebellion and who last week publicly apologised to the PM for making his campaign personal.

The ex-minister told GMTV's Sunday Programme in a pre-recorded interview that Mr Brown was "dead in tune with the country and should fight the corner" on the 42 days issue.