Peter Robinson has issued an ultimatum to the British Government over the issuing of letters to on-the-run paramilitary suspects.
The First Minister has also asked the Speaker to recall the Northern Ireland Assembly on Friday, after claiming the Government deal that saw IRA terror suspects assured they would not be prosecuted also involved the granting of royal pardons.
Mr Robinson had already threatened to resign unless a public inquiry is ordered into the controversy that has been triggered by the collapse of the Hyde Park bomb case.
Following a meeting with Secretary of State Theresa Villiers at Hillsborough Castle on Wednesday night, the DUP leader said the contents of a motion he would put before the Stormont Assembly during a specially convened session on Friday would depend on how the Government responded to his demand.
He has effectively given the Government a 24 hour deadline.
Robinson sparked a potential constitutional crisis when he threatened to quit unless there is a judicial inquiry into the secret letters sent to IRA men who were on-the-run.
He claimed he had no knowledge such letters were ever written and said he wasn't prepared to remain in his role after being "kept in the dark by Her Majesty's government about matters relevant to Northern Ireland".
Mr Robinson said he now understood pardons had also been granted.
"It appears that we are not just dealing with on-the-runs who received letters but we are also dealing with people who received the Royal Prerogative of Mercy, that indicates there were offences involved," he said.
"So we are not talking just about people who it is believed that the police did not have sufficient evidence to make a prosecution stick - that makes it a very serious matter."
Mr Robinson is consulting other parties on the wording of a motion to put before the Assembly.
His anger followed the collapse of the trial of suspected Hyde Park bomber John Downey.
The former IRA man from Donegal walked free from court on Tuesday after it emerged he was mistakenly told in a letter in 2007 that he was no longer a wanted man.
Earlier on Wednesday evening, Sinn Fein's Gerry Kelly blasted Mr Robinson as "foolish" for saying he was kept in the dark about the on-the-run deal.
He told Channel 4 News that Unionists must have known about the deal.
"It was very public and for the Unionists to claim they knew nothing about it is false. (Robinson) knew about the OTR situation, he knew they were crucial to the peace process and the political process," he said.
"He is foolish and needs to be careful as a political leader painting himself into a corner on the issue."
Meanwhile Peter Hain, who was Northern Ireland secretary when the letters were sent, has said he makes no apology for the letters assuring 187 people they would not be pursued for prosecution.
Writing in the Guardian on Wednesday, he criticised what he called "loose talk of 'deceitful deals' by Tony Blair's government" and said the OTRs deal was necessary for peace, "just as it was necessary to do 'side deals' with Ian Paisley's DUP, which I also did."
"The 1998 prisoner releases left an anomaly of more than 200 terrorist suspects "on the run", completely outside the reach of our justice system, concerning terrorist offences before 10 April 1998, who could face jail – yet who, had they been in prison at the material time, would have been part of that early-release scheme," he wrote.
"This was important to Sinn Féin because it needed to get all active republicans along with them behind the peace process. With some freed after Good Friday, but others potentially facing arrest and prosecution, the whole process could have been badly disrupted."
Mr Hain slammed Conservative politicians for "opportunistically rewriting history" and said at the time, names submitted were "painstakingly assessed" by the PSNI.
Attorney General Dominic Grieve stood by his decision to charge Downey despite the collapse of his case yesterday due to what victims said was a "monumental" police error.
But Defence Minister Anna Soubry, a former barrister, said there was no chance of a judicial review.
"You can't judicially review the decision," she told BBC Radio 4. "You can appeal it, the prosecution can appeal it. Dominic Grieve has made it clear the CPS has taken the view that these are not the right circumstances to appeal it.
"So, with great respect to Peter Robinson, who is quite right to be very angry, absolutely right to be angry, but we are in a very, very unpleasant, bad situation and, unfortunately, I cannot see any way back from where we are now."
Of the 187 letters, Ms Villiers has said 38 were issued since the coalition Government came to power in 2010 - a period after justice powers had been devolved back to Stormont.
Northern Ireland's Justice Minister David Ford tonight said it was "deeply disturbing" that letters continued to be issued by the NIO when responsibility for justice had been transferred to the power-sharing executive in Belfast.
"The first I became aware of this scheme and the associated letters issued was after the Downey court decision and shortly before it became public," he said.
"It was never introduced to me either before, at the point of devolution or since devolution in April 2010.
"Comments made by the Secretary of State in the House of Commons that letters have been issued since the devolution of justice are deeply disturbing. I have demanded a meeting with the Secretary of State and will be meeting her later this evening to clarify who has signed these letters.
"What I do know is that none of these letters have issued from the Department of Justice. What we don't know is what the implications may be for prosecutions and for our crucial efforts to find political consensus on how to deal with the past.
"It is important that the victims of this, and all the other atrocities, are remembered and sensitivity observed."