The former health secretary Frank Dobson is rallying opposition among Labour MPs for a full-scale revolt against Gordon Brown's proposal to allow suspected terrorists to be detained without charge for up to 42 days.
Mr Dobson, chairman of the Labour backbench civil liberties group, is a supporter of Mr Brown but is determined to stop the measure which he believes will undermine basic rights laid down in the Magna Carta.
He has organised a meeting for the 49 Labour dissidents who voted against the proposal to extend detention without charge to 90 days when Tony Blair suffered his first Commons defeat. The group has been whittled down by appointments to the lower rungs of the ministerial ladder in the Brown government, but the meeting will give the whips a clear warning of the size of the revolt ahead.
"Even George 'Guantanamo Bay' Bush has got only 48 hours' detention without charge in the United States and yet we have already got detention without charge for 28 days. I think that is quite enough," said Mr Dobson. "We have already got the longest period of detention without charge in the democratic world. I cannot see any reason for making it longer. I have been the principal advocate for allowing suspects to be interviewed after being charged. That should be sufficient."
Mr Dobson's opposition to the measure outlined by the Home Secretary, Jacqui Smith, will cause alarm among the whips who had been hoping to avoid a major rebellion. Ms Smith will appear before the Commons Home Affairs Committee on Tuesday to appeal to it to support 42-days' detention before it delivers its report on the legislation.
In a letter to fellow dissidents calling the meeting for Tuesday, Mr Dobson says he wants to "see what we can do to persuade ministers to accept an alternative to a further extension which we can all support".
The dissidents are also expected to include Mark Fisher, a former arts minister. John McDonnell, the chairman of the left-wing Campaign Group of Labour MPs, said in a GMTV interview to be broadcast tomorrow that a number of Labour MPs were "quite angry" because the Prime Minister had "bounced" them into the proposal. "Most of us thought those discussions were still going on and we'd meet after Christmas and then we'd arrive at a consensus."