A victims' delegation has handed in a petition to Downing Street against proposals to allow fugitives from Northern Ireland to return home.
The petition was handed in to Downing Street
It urged the government to justify the "staggering contradiction" between its proposals for Northern Ireland and its planned 90-day anti-terror law.
The group was accompanied by DUP MPs who have refused to back the NI plan.
Aileen Quinton whose mother died in the 1987 Enniskillen bombing said victims felt it was an "amnesty" to terrorists.
The proposals, which were introduced in the House of Commons on Wednesday, cover up to 150 people wanted for crimes committed before the Good Friday Agreement in 1998.
Their cases would be heard by a special tribunal, but if found guilty they would be freed on licence without having to go to jail.
Ms Quinton said the government had under-estimated the difficulties it would have in passing the legislation.
She read out the text of the letter the group had handed in to the prime minister.
People suspected of being involved in terrorism could return
"We are writing to you to request a meeting face-to-face so that you can explain to us how you can justify this legislation," it said.
"You claim that victims are at the heart of your policy in Northern Ireland. If that is so then you should have no difficulty in meeting with us."
The DUP MPs who went to Downing Street included Jeffrey Donaldson, William McCrea and Iris Robinson.
Mr Donaldson said there were no circumstances under which the DUP would support the law, calling it a "betrayal" of the victims in Northern Ireland.
He said: "There really is no stomach for this legislation.
"I think there is a real prospect now that it will be defeated in the House of Commons as well (as the Lords)."
A DUP delegation earlier met NIO minister David Hanson and reinforced their opposition to the bill.
Meanwhile, the contentious issue was high on the agenda when an Ulster Unionist delegation met Tony Blair in Downing Street on Thursday.
Party leader Sir Reg Empey accused the government of "rubbing salt mercilessly in the wounds of the victims of terrorism".
Sir Reg said that the UUP had made it plain to Mr Blair it would fight the legislation.
He also criticised the "contradiction" of the government in bringing the Northern Ireland Offences Bill forward on the same day it had tried to push through powers to detain terror suspects without charge for 90 days.
The UUP's sole MP, Lady Sylvia Hermon, said the government's move had been "deeply offensive".
She confirmed, however, that she had voted with the government in favour of the 90-day detention plan, after taking adviceon the matter from Chief Constable Sir Hugh Orde.