MPs are set to debate controversial government plans to allow paramilitary fugitives to return to Northern Ireland without serving a prison sentence.
Fugitives would be freed on licence no matter how serious their crimes
Many of the fugitives have never stood trial and would not do so under the new law, due to have its second reading.
Tony Blair has said it is needed to restart the stalled political process.
But Unionists and terror victims have condemned the plans, which cover up to 150 people wanted for crimes committed before the 1998 Good Friday Agreement.
Under the bill, paramilitary fugitives would be freed automatically on licence on their return to Northern Ireland.
There would be a formal finding of guilt and they would have a criminal record, but they would not have to appear in court or spend time in custody.
BBC Northern Ireland correspondent Kevin Connolly said: "The sticking point for many victims of terrorism this time is this - on-the-run paramilitaries will not even have to appear before a public tribunal before a finding of guilt is issued against them and they are granted their freedom on licence with the stroke of a judicial pen."
On Tuesday, Liberal Democrat leader Charles Kennedy said the scheme had "serious problems".
"There are serious problems with a scheme which doesn't even require an accused person to appear in court.
"What does that say about our attitude to justice and what kind of signal does that send to their victims?" Mr Kennedy asked.
"We have had serious objections since this was first suggested in April 2001. It is time the prime minister started listening."
Mr Blair said it was a difficult issue but needed to be addressed.
"I really believe it's best to get this issue out of the way so we can get on with building an executive and an assembly that are back up and running again," he said.
Mr Blair defended the bill to a Commons' committee on Tuesday
"If it hangs over this process much longer, it won't do any of us any good."
If the legislation is passed, paramilitary fugitives would have their cases heard by a special tribunal, but, if found guilty, would be freed on licence without having to go to jail.
"The on-the-run thing is very, very difficult," Mr Blair told the Commons Liaison Committee on Tuesday.
"It's true the political parties in Northern Ireland are never going to agree with this legislation.
"I think they all actually know this has to be done.
"It doesn't surprise me that they are going to oppose it very vigorously and say some very harsh things about the government.
"But I also genuinely believe we need to get this out of the way and dealt with so we can get on with the really tough thing, which is building consent for the institutions."
However, Mr Blair acknowledged that it was an "uncomfortable issue" for many.
"I don't minimise the anger there will be in some quarters or the anguish if you are the relative of a policeman in Northern Ireland who was killed," he said.