The government will compromise to avoid defeat over plans to extend pre-charge detention for terror suspects from 28 days to 42 days, the BBC understands.
The government is preparing to offer Labour MPs a major concession to avoid losing a vote on terror detentions, the BBC has learned.
It comes as rebel Labour MPs threaten to vote against the proposed extension.
Ministers want to extend the limit suspects can be held without charge to 42 days, which many Labour MPs oppose.
Judges would be involved earlier in the process with greater clarity over the "exceptional circumstances" which would allow 42-day detention to be used.
To avoid losing a Commons vote, the government is to suggest halving the period during which police can enact these extra powers from 60 to 30 days.
"We remain in consensus mode. This is too serious to leave to partisan politics," said minister Tony McNulty.
The BBC's James Landale said this was a "significant concession".
Prime Minister Gordon Brown has said he would rather "do the right thing" and lose, than back down on the 42-day limit.
About 50 Labour MPs are believed to be ready to vote against the government in the Commons next month unless changes are made.
'Mickey Mouse compromises'
The series of amendments expected to be tabled would allow Parliament to vote within seven to 10 days on the decision to extend the detention, rather than 30 days at present.
There would also be an outline of the circumstances which would trigger increased detention.
Even with these additional concessions, 42 days would not be seen to be lawful Andrew Dismore, Labour MP
It is hoped that up to half of the 50 MPs will be placated by these measures, the BBC understands.
However, sources among the rebels have branded these "Mickey Mouse compromises" which would not fundamentally change the nature of the legislation.
And Labour backbencher Andrew Dismore, who chairs Parliament's joint committee on human rights, said the concessions ignored the fundamental "right to liberty".
"The fact is that even with these additional concessions, 42 days would not be seen to be lawful," he told BBC Radio 4's The World at One.
We're only asking for that reserve power, not some kind of bull-in-a-china-shop approach Tony McNulty, Home Office minister
"There are obligations under the European Convention of Human Rights (ECHR) in relation to liberty, and if you are going to go beyond that, then it has to be something very, very serious indeed."
But Mr McNulty, a minister at the Home Office, maintained: "The notion that somehow the 28 days, or going beyond 28 days in these extraordinary circumstances, doesn't comply with our ECHR obligations is simply not true."
He said it was clear there were times "where there might be a need, in truly exceptional circumstances, to go beyond the 28 days".
"We're only asking for that reserve power, not some kind of bull-in-a-china-shop approach going up to 42 days on a universal basis," he told the BBC.
The government also wants to secure the support of the nine Democratic Unionist Party MPs.
One possibility might be with offers of seats on the Intelligence and Security select committee.
Or it could be by ensuring income from the sale of surplus Army land in Northern Ireland stays in the province, rather than going to the Treasury.
It is understood an even more radical compromise was discussed in which the 42-day limit would be triggered only in cases of emergency where there was evidence of multiple terrorism plots.
However, it was felt this would appear to much like a climbdown, following the recent rebellion against the abolition of the 10p tax rate and protests by hauliers over the soaring cost of fuel.
