Home Secretary Charles Clarke faces increasing pressure to reveal the Attorney General's advice on the government's anti-terror bill.
Mr Clarke had to apologise to MPs
Mr Clarke apologised to the Commons on Thursday for telling MPs Lord Goldsmith had approved holding suspects for up to 90 days without charge.
He will hold cross-party talks at the weekend to seek an agreement on the maximum detention period.
Tony Blair has warned it is not "an issue to play around with".
Liberal Democrat home affairs spokesman Mark Oaten said there was "uncertainty" over the bill's compliance with European human rights law.
Currently the maximum time suspects can be held without charge is 14 days.
On Wednesday, Mr Clarke agreed to all-party talks on the detention of suspects to head off a backbench revolt on the issue.
This happened after it had become clear the government risked losing a vote on an amendment setting a 28-day limit.
Mr Clarke said he would seek agreement and bring forward new proposals next week.
Last month Lord Goldsmith's spokesman was quoted as saying: "He believes the case is there for longer than 14 days but is not convinced he has seen a case for 90 days."
Mr Oaten said: "Whatever the normal arguments about the confidentiality of the Attorney General's advice, this announcement from the Home Secretary relates to views that are already in the public domain.
"On such a controversial measure, it is now in everyone's interests for the advice to be published."
In the Commons on Thursday Mr Clarke had to admit the opinion he had quoted "did not come from the Attorney personally".
He also apologised for breaching a convention not to disclose any of the legal advice given to ministers.
Conservative former chancellor Kenneth Clarke said: "We now no longer know what the Attorney General's opinion is, despite the press speculation there has been that he is deeply disturbed."
Former health secretary Frank Dobson said the prime minister had put the home secretary "in an impossible position".
Meanwhile, a senior police officer has denied criticising government anti-terror plans, after Downing Street moved to distance itself from comments he reportedly made at an awards ceremony.
Metropolitan Police Deputy Assistant Commissioner Brian Paddick was quoted by the London Evening Standard as saying: "We have to be aware of unintended consequences of legislation in terms of whether it affects people's willingness to come forward."
In a statement, Mr Paddick said he had not made "any statement nor did I offer any opinion about the proposed anti-terrorism legislation".
He added: "What I did say was the importance of reassuring communities by explaining the safeguards contained in legislation.
"Communities are an important source of information about suspected terrorists and it is important to maintain public confidence. "It is only when politicians, police and communities work together that terrorism will be defeated.
"As a professional police officer and a senior member of the Metropolitan Police Service I support the view that extension of detention to 90 days is necessary in difficult, complex and sensitive terrorism cases where it would not otherwise be possible to carry out a full and proper investigation and to bring terrorists to justice."