Sinn Féin claims the disclosure by police that they have found IRA intelligence documents naming senior Conservative politicians is part of a continuing Special Branch "cover-up" over the Castlereagh break-in. Security sources have dismissed the claim.
This latest twist to the mystery surrounding the Castlereagh raid could have damaging implications for the political process. The Ulster Unionist Party last night threatened to take sanctions against Sinn Féin over the disclosure. The party's ruling executive warned it would take "appropriate action".
"And if the IRA did do Castlereagh, then we will be seeking the expulsion of Martin McGuinness and Bairbre de Brún from the Executive," said a senior executive member.
On Castlereagh, the only thing clear last night was that either provisional republicans or senior security figures were engaged in a detailed exercise in disinformation.
Notwithstanding this credibility struggle involving Sinn Féin and the IRA versus the police Special Branch, the acting head of the Police Service of Northern Ireland (PSNI), Mr Colin Cramphorn, expressed confidence that the IRA ceasefire remained intact.
The Northern Secretary, Dr John Reid, also said there was no evidence of any planned IRA return to violence.
"There is no indication that the IRA is either about to or intending to recommence its campaign," he said.
The IRA intelligence papers were discovered following raids on republican homes and offices in the immediate aftermath of the St Patrick's Day theft of Special Branch documents from Castlereagh police station, according to security sources.
This IRA material contained information on senior Tory politicians, British army installations and loyalist figures. According to security sources, it was updated as recently as early March.
These documents are not the papers stolen from Castlereagh. The Castlereagh material contained names and addresses of Special Branch officers, the code names of their informants and addresses of republican and loyalist figures, including Progressive Unionist Party leader Mr David Ervine.
Security sources again insisted that the Castlereagh break-in was the work of the IRA despite repeated denials by the IRA and Sinn Féin.
Sinn Féin MLA Mr Gerry Kelly went further this week by stating that not only was the IRA not involved, but that it did not have the information contained in the documents.
PSNI chief Mr Cramphorn said, however, that while there were other lines of investigation "IRA involvement is a major line of inquiry".
Security sources confirmed a BBC report that police believe an analysis of calls from mobile phones and coin boxes in west Belfast around the time of the Castlereagh raid could be critical in determining who was responsible.
Police also believe the Castlereagh documents, which could threaten the security of Special Branch officers, their families and their informants, were moved from Belfast to Derry and then to the Republic.
They believe that a chef who moved to New York, who formerly worked at Castlereagh and who reportedly was in the building on the day of the raid, could be central to their inquiries.
The man was questioned in New York about the theft by senior PSNI officers and by the FBI, according to a senior security source. Some IRA sources also confirmed that a man with republican sympathies worked at Castlereagh.
Sinn Féin continued to insist yesterday that republicans were not involved in the break-in and said that details released about IRA intelligence gathering on Tory politicians was designed to further muddy the waters over Castlereagh and damage the peace process.
"The facts are that this raid was carried out by elements within British military intelligence or the Special Branch and has nothing whatsoever to do with republicans," said Sinn Féin MLA Mr Conor Murphy.
Should these denials be proved wrong, it would be highly embarrassing for Sinn Féin. It would raise questions about the stability of the IRA ceasefire and Sinn Féin's commitment to working the Belfast Agreement.
However, if it is impossible for the police to find sufficient evidence to procure convictions, then irrespective of the suspicions of IRA involvement, it could be tactically safe for Sinn Féin to continue denying republican involvement. Equally, any evidence that supported the republican contention of a Special Branch cover-up would be very damaging for the fledgling PSNI.
The Ulster Unionist Party has called for an urgent meeting with Mr Cramphorn to discuss the issue. Anti-agreement Ulster Unionist MP Mr David Burnside said if the IRA was responsible, Dr Reid would have no option but to declare the IRA in breach of its ceasefire.
