The killers of an Irish police officer were to be released as part of a deal designed to restore Northern Ireland's power-sharing assembly last year, the BBC has learned.
Murdered Garda Jerry McCabe
Detective Jerry McCabe was killed and another officer wounded during an attempted robbery at Adare in County Limerick in June 1996.
Four men were later convicted of the manslaughter of the officer and Sinn Fein has been calling for their release under the terms of the Good Friday Agreement.
On Friday, the Department of Justice in Dublin said: "The government has always made it clear that it would not authorise any such release in the context of continued Provisional paramilitarism.
"The goverment's position has not changed and will not change."
Sources have told the BBC that the Irish Government agreed to the prison release as part of the deal to restore the devolved assembly at Stormont in October 2003.
Their release would have been seen as a significant concession to republicans.
A potential deal to move the Northern Ireland political process forward stalled in October over the issue of IRA weapons.
Unionists complained that not enough information had been provided on the IRA's third act of decommissioning.
On Friday, Ulster Unionist leader David Trimble said he knew nothing about an alleged plan, but questioned the timing of the revelation.
Mr Trimble told the BBC that, if true, this vindicated his decision last autumn to call off a deal.
Sinn Fein's Martin McGuinness said the four men jailed for the killing qualified for release under the terms of the Good Friday Agreement.
He said: "It's our view that they should be released but I'm not going to
make any comment about what the two governments may or may not have agreed. It is our view that this case needs to be resolved."
Mr Trimble said he considered any secret deal a devious action
Alex Attwood of the SDLP said killers of Garda McCabe did "not have the benefit" of early release under the Agreement.
"If the speculation is true, it is very revealing about what Sinn Fein negotiate about - their own needs and self-interest."
DUP deputy leader Peter Robinson condemned the reported deal.
"It would seem that the Irish Government are now taking action consistent with the British Government's consistently wrong attitude to the early release of terrorist killers," he said.
"I am deeply disturbed that the release of McCauley, Walsh, Sheehy and O'Neill is part of last autumn's secret deal involving the UUP and Sinn Fein/IRA - a deal whose full details still remain hidden from the people of Northern Ireland."
The leader of the main opposition party in the Republic has called on the Irish Prime Minister Bertie Ahern to make a full statement about the allegations.
Fine Gael leader Enda Kenny said: "The statement from the Department of Justice raises even more concern, as it fails to deny the central allegation that the government was prepared to release the killers of Jerry McCabe, despite their firm promises to the contrary."
Garda Representative Association spokesman Paul Brown told the Irish state broadcaster, RTE, that the organisation knew nothing of such a deal.
Mr Brown said the association would be taking the matter up with the government.
The killing of Garda McCabe happened four months after the breakdown of the first IRA ceasefire in 1996 and initially the IRA denied any involvement.
It later admitted that individual members were involved - the IRA said "in contravention of its orders".
Since last October Sinn Fein have been demanding that the British and Irish Governments implement what was agreed.
On the claim that the prisoners, who are held in Castlerea prison in County Roscommon, were to be freed, a spokesman at the Department of Justice in Dublin said they had no comment to make.