Charles Clarke's plans to allow judges to detain terror suspects without trial may still breach human rights laws, a committee of MPs and peers has warned.
The bill has been subject to angry debate in the Lords
The Joint Committee on Human Rights says changes to the Prevention of Terror Bill may not go far enough.
The home secretary has given way over plans to allow him to impose the house arrest "control order" on a suspect, allowing judges to make them instead.
The Home Office says the bill does comply with human rights laws.
The House of Lords has approved government amendments to the bill, but opponents are expected to press for more concessions when the debate resumes next week.
Veteran Labour MP David Winnick, one of 62 party rebels to vote against the bill, said he will do so again unless Mr Clarke makes more concessions.
And former law lord Lord Ackner warned that the judiciary had profound misgivings about the measures.
He said it was clear from the drafting of the bill that the defendant was not to be told about the case against him or the basis of the decision.
"It sounds so much better to say 'we'll leave it to the judge', but if you leave it to the judge without his being able to exercise the obligations of due process, you are not leaving it to the judge at all," he told BBC Radio 4's The World at One.
The government wants to get new laws through Parliament by 14 March, to replace the detention of foreign terrorist suspects without trial, which the law lords have ruled against.
But MPs and peers on the cross-party committee said the bill's rapid progress did not give them enough time to scrutinise its human rights compatibility.
And they asked whether the extent of judicial involvement would meet the European Convention on Human Rights' requirement that "deprivations of liberty must be lawful".
However a Home Office spokeswoman said the government was satisfied its bill complied with human rights laws "in all respects"
"We believe the bill strikes the right balance between protecting the security of the nation and observing civil liberties," she said.
The committee also welcomed the home secretary's pledge to involve judges in imposing higher level "control orders" for house arrest.
But it said the procedure gave no chance for a lawyer to make a defence case at an early stage and said it uses too low a threshold of evidence.
And they said judges, not politicians, should issue lesser "control orders" such as tagging and banning the use of mobile phones.
Concerns about the possibility of using information against suspects which had been secured by torture was also raised.
This is the final report of the Joint Committee on Human Rights, which produced a preliminary assessment late last month.
HAVE YOUR SAY
All decisions pertaining to the liberty of the individual should be made by a judge, never by a politician
Mr Clarke has questioned whether the Tories would take responsibility for not putting a control order on someone who was dangerous and who then went on to "commit a terrible act".
The Tories have said they will back the bill, but shadow home secretary David Davis expressed reservations.
"It is simply wrong under British law, British tradition, British freedom and British justice," he said.
Liberal Democrat leader Charles Kennedy has said ministers would have to make significant further changes if the bill was to get through the Lords.