LONDON - Britain is expected to unveil plans to extend the time terrorism suspects can be held without charge on Thursday but will offer a compromise to opponents that would give parliament a greater say, media reports said.

Under the new powers to be unveiled by Home Secretary Jacqui Smith, lawmakers will have the final say on whether police can hold suspects for longer than 28 days allowed under the current law, the reports said.

Since taking over from Tony Blain in June, Prime Minister Gordon Brown has said the powers needed to be extended, possibly to as much as 58 days, to allow police to deal with complicated terrorism investigations.

But he has been forced to backtrack when faced with growing opposition, not just from political opponents and civil rights groups but from prosecutors and those within his own Labour Party.

The current 28-day limit was brought in as a compromise two years ago after Blair suffered his first defeat in the House of Commons when Labour MPs rebelled against plans for a 90-day limit.

Instead, parliament agreed on a compromise deal which means they can be detained for up to 28 days, which civil rights groups argue is already longer than in any other comparable democracy.

Ministers concede that no case has so far required more than the 28-day limit but said detectives had been pushed to the brink over the suspected plot to blow up trans-Atlantic airliners last August.

Two of the suspects were charged on the 28th day of their detention.

According to newspapers, the latest proposal would mean that MPs would vote on individual cases on whether detectives could hold suspects for longer, with reports suggesting a new upper limit of 42-days has been mooted.

While police and the independent reviewer of government terrorism laws say there could be occasions when a longer pre-charge detention period is needed, many senior figures remain unconvinced.

Last month, former attorney general and government top lawyer, Lord Goldsmith, and Ken Macdonald, the Director of Public Prosecutions, both said they were happy with the current situation.

Both the opposition Conservatives and Liberal Democrats have said they had seen no evidence produced by the government to justify a longer period of detention.

Shami Chakrabarti, director of civil rights group Liberty, said she believed that cross-party consensus had been possible but it appeared the government was playing politics with security.

"I for one still thought we were part of a constructive and friendly and ongoing process and then yesterday evening the process had stopped. My interpretation of that being consensus is not actually sought," she told BBC radio.