The Government has hardened its line on Sinn Féin and the IRA in the aftermath of the murder of Belfast man Kevin McGuigan with the Minister for Justice asking the Garda Commissioner to conduct a "fresh assessment" of the activities of the Provisional IRA in light of the PSNI investigation into the murder.

In a statement, Frances 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."

Ms Fitzgerald added: "As was clear from what the Chief Constable said at the weekend there are no simplistic answers about the continued existence of PIRA. 

"To simply say PIRA continues to exist as if nothing has changed would be quite wrong. To be blunt, making organisational judgements is complicated by the fact that many, if not all, members of PIRA were members of Sinn Féin.  

"The information available to me is consistent with the reports of the Independent Monitoring Commission.

"These said PIRA remained on an exclusively political path, the so-called 'military' departments had been disbanded and the former terrorist capability had been lost, the organisation was not involved in illegal activity, although contrary to instructions and for personal gain some individual members were."

Ms Fitzgerald said this mirrors what gardaí have said about the activities of the PIRA in the Republic.

The minister said "one of the issues which will be taken into account is what the PSNI have been learning about any PIRA structures as a result of that investigation".

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 Féin can wash their hands of responsibility for that. It is an inevitable legacy of the brutal campaign which PIRA waged."

Sinn Féin TD Brian Stanley has said the party welcomes the review announced by Minister Fitzgerald which he said would show the IRA had stood down and did not exist.

Mr Stanley said there may be other groups masquerading as "some kind of IRA" such as the Real IRA or the continuity IRA but they should disband and go away as they had no contribution to make.

Meanwhile, Tánaiste Joan Burton has said it is clear that communities continue to be at risk from an organisation linked to "murder and racketeering".

Ms Burton said Sinn Féin could not deny all knowledge of IRA criminality or its existence.

In a statement, she said: "While I accept the assessments of the PSNI and the Garda that the Provisional IRA is no longer involved in terrorist activity, that is of little comfort given that members of the organisation are clearly involved in serious criminality.

"In that respect, while everyone acknowledges that Northern Ireland no longer faces the kind of paramilitary threat that the IRA once posed, its communities are still at risk from an organisation linked to murder and racketeering.

"This is an insidious threat to Northern Ireland's future as a healthy, stable democracy, and therefore a threat to the whole of this island.

"It is therefore not good enough for Sinn Féin to deny all knowledge of Provisional IRA criminality and pretend it simply doesn't exist.

"And it's particularly reprehensible for Gerry Adams to be triumphalist about the IRA supposedly remaining 'undefeated' while communities suffer from continued criminality at the hands of members of the organisation."

Mr Adams, Sinn Féin's president, has said the killings of Gerard 'Jock' Davison and of Mr McGuigan were wrong.

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

Northern Secretary Teresa Villiers yesterday said she was not surprised by police beliefs that the IRA still existed. 

But she added that there was no evidence of IRA paramilitary or terrorist activities.

The Ulster Unionist Party has said that leaving the Stormont Executive was an option it would consider over the next two days.

Fianna Fáil leader Micheál Martin has said the governments on both sides of the border seem to be implicitly accepting the existence of the IRA.

He said by saying it does not exist in the way it did in the past they are almost condoning it.

Speaking on BBC Radio Ulster’s Good Morning Ulster, Mr Martin said he was taken aback by Ms Villiers saying it came as no surprise to her that the IRA still existed.

Mr Martin said the manner in which Ms Villiers responded to the crisis "left an awful lot to be desired".

In relation to unionists considering their options in terms of the Stormont executive, Mr Martin said it is a very difficult situation for all of the parties in the executive.

He said the peace process belongs to everybody and that at times it becomes very frustrating when serious questions are raised that the response is "you are going to damage the peace process".

Analysis: Political Correspondent David Davin-Power

This is a very political statement from Minister for Justice Frances Fitzgerald, and taken in conjunction with earlier remarks from Tánaiste Joan Burton, you can see that the Government is ratcheting up the pressure on Sinn Féin.

Nothing concrete may emerge from this investigation but there was some surprise at the mild tone of Frances Fitzgerald’s remarks at Béal na Bláth at the weekend.

She was singled out in one particular national newspaper for criticism.  

Now you see a more political response from the Government – a blistering attack on Sinn Féin and Gerry Adams, with Fitzgerald signalling out his knowledge of what the IRA membership had been involved in after the ceasefire.