Northern Ireland Secretary Theresa Villiers said the police's belief that the Provisional IRA (PIRA) still exists did not come as a surprise to the British government.

Villiers said in her time in office she had been aware some of PIRA remained in place – but there was no evidence it was involved in any paramilitary or terrorist activity.

Her comments came after Northern Ireland’s police Chief Constable George Hamilton said PIRA members were involved in killing an ex-IRA man.

Across the border in the Republic, concern has also been expressed in the Dublin government over the prospect that the PIRA still exists despite a repeated claim by Gerry Adams this week that it has “gone away.”

Meanwhile, the Ulster Unionist Party has announced that it is leaving the Stormont Executive. Party leader Mike Nesbitt said, “We need credibility if we are going to maintain these institutions of government. We need honesty and we need parties that are prepared to build trust with us.”

The Democratic Unionist Party has also questioned Sinn Fein’s participation in government after the police chief said the IRA still exists.

Controversy erupted over the murder in Belfast of 53-year-old father of nine Kevin McGuigan outside his home as part of what police believe was a “fall-out” in Republican circles.

His murder is believed to have been a revenge attack following the murder in May of Gerard “Jock” Davison, a former PIRA commander. He was shot and killed on May 5. Davison was quizzed about the murder of Robert McCartney in January 2005 but was released without charge.

Police boss George Hamilton said an infrastructure exists at a senior level of the PIRA, but that it is not on a “war footing.”

Villiers said she understood that a number of the organizational structures of the PIRA still exist but that there is no evidence of its involvement in terrorism or paramilitary activity.

In Dublin, Justice Minister Frances Fitzgerald has asked Garda (police) Commissioner Noirin O’Sullivan to conduct a “fresh assessment” of the activities of the PIRA in light of the PSNI investigation into the murder of McGuigan.

In a statement on Tuesday Fitzgerald said, “Recent developments are of considerable concern, but what we need to do now is establish all the current facts and that is what is happening in the rigorous investigation being carried out by the PSNI.”

She added, “There is no doubt that people who have been associated with PIRA have been – and continue to be – involved in the most serious crime, and neither Gerry Adams nor Sinn Fein can wash their hands of responsibility for that. It is an inevitable legacy of the brutal campaign which PIRA waged.”

Tanaiste (deputy prime minister) Joan Burton said that while she accepted the assessments of the PSNI and the Garda that the Provisional IRA was no longer involved in terrorist activity, that was of little comfort given that members of the organization were clearly involved in serious criminality.

Sinn Fein President Gerry Adams said the killings of Davison and of McGuigan were wrong.

He said those involved did not represent republicanism, were not in the IRA and that the IRA had “gone away.”