Sinn Fein's ministers should stand down from the powersharing executive in order to avert the suspension of devolution, a leading Ulster Unionist has said.

Sir Reg Empey said the republican movement had a case to answer over the recent allegations of IRA intelligence gathering within the Northern Ireland Office.

"I would be calling today for Sinn Fein, if they really care about the institutions, to stand down from the executive voluntarily," he said.

Sir Reg Empey: "Republican movement has a case to answer"

"This would allow the institutions to survive while all of this is looked into and resolved, because there are outstanding matters that do require to be resolved."

Speaking on BBC's Inside Politics programme on Saturday, Sir Reg said there had been a series of events involving republicans linked to the IRA.

"They all send out the signal that the transformation that the Good Friday Agreement is built around is not taking place."

Speaking on the same programme, SDLP leader Mark Durkan said there was a problem over confidence and trust.

"I don't think that Sinn Fein can go on saying that every time there is a crisis or a problem that it is all the fault of rejectionists," he said.

"The difficulty is that many people who have embraced this process, who have done a lot and contributed to this process, have taken risks for this process... end up tripping over other incidents which give people serious cause for concern that the transition from violence by the republican movement isn't complete enough."

'Ludicrous'

Sinn Fein president Gerry Adams said Ulster Unionist leader David Trimble had no basis for his demands for the expulsion of Sinn Fein from the executive.

Speaking in Dublin on Saturday, he said: "Despite his protestations to the contrary Mr Trimble favours suspension.

"Mr Trimble's attack on the proposition that the two governments must step in to ensure that those important aspects of the agreement that can be implemented are implemented is ludicrous.

"He knows that the unionist exodus from the institutions leaves no other option."

Irish Foreign Minister Brian Cowen said there was a "common determination" by the British and Irish governments to ensure the agenda of the Good Friday Agreement was fully implemented if the assembly's suspension went ahead.

"That is the best prospect for political stability - and the hope that we will see put away for ever the spectre of paramilitarism and sectarianism that has bedevilled this process for far too long," he said.

Fourth time

On Friday, the two Democratic Unionist Party ministers resigned from the Northern Ireland Executive ahead of the likely suspension of the powersharing government.

Regional Development Minister Peter Robinson and Social Development Minister Nigel Dodds resigned over allegations of IRA spying within the Northern Ireland Office.

Peter Robinson: Resigned from the executive

Earlier on Friday, Northern Ireland First Minister David Trimble held talks with Irish Prime Minister Bertie Ahern in Dublin to discuss the crisis in the province's political process.

Speaking after the meeting, Mr Trimble said that suspension was "very much a second best option".

Government sources told the BBC on Thursday the Stormont Assembly would be suspended for the fourth time next Monday.

Mr Trimble added that he wanted the government to make "tackling the underlying problems" in the political process the first priority, rather than focussing on the mechanics of the situation.

Last week, the Ulster Unionist leader said his party would pull out of power sharing next week unless the UK Government proposed the expulsion of Sinn Fein from the Stormont administration.

It is understood two extra ministers will be appointed to the Northern Ireland Office to take over the work of the executive, once direct rule from Westminster is re-introduced.

Friday's meeting in Dublin between Mr Trimble and Mr Ahern was one of a series involving the British and Irish governments and the political parties in recent days.

On Thursday, Sinn Fein president Gerry Adams said suspension of the executive would be a mistake after meeting Tony Blair in Downing Street.