BBC Northern Ireland political editor Mark Devenport explains the context of the row and its impact on the search for peace.

What have been the key developments this week ?

On Monday the PSNI Chief Constable Hugh Orde apologised for the high profile style of the police search of Sinn Fein's offices at Stormont but insisted that the operation had been necessary.

On Tuesday the DUP leader Ian Paisley confirmed that his party's two ministers in the power-sharing executive, the Regional Development Minister Peter Robinson and the Social Development Minister Nigel Dodds, would resign. Their resignations take effect at noon on Friday.

Also on Tuesday the Ulster Unionist leader David Trimble gave the government one week to take action. He said that if the government had not tabled a motion at the Northern Ireland Assembly calling for Sinn Fein's exclusion from government by the start of next week the Ulster Unionist ministers would quit.

The government wouldn't spell out which course of action they would take - insisting that they wanted to hold talks with nationalist politicians and the Irish Prime Minister Bertie Ahern before deciding their strategy.

What are the options over the next seven days ?

There are three options:

• The government could table a motion calling for the exclusion of Sinn Fein on the grounds that the republicans aren't abiding by the Mitchell principles on peace and democracy. Unionists support this approach, but it's likely to prove unpopular with the Irish government and the nationalist SDLP.

• The government could dissolve the Assembly and call early elections - but a hard fought election campaign could further damage the already fragile political centreground.

• The most likely course of action appears to be suspending the devolved institutions. Both John Reid and his predecessor Peter Mandelson have used suspension before - but this time a suspension could last longer than in the past.

Sinn Fein will continue to hold seats in the Assembly on the basis of the electoral mandate they won in 1998. However, they would be exluded from holding ministerial office in the power sharing Executive.

The Executive could continue if it was still backed by the SDLP who hold the majority of nationalist seats in the Assembly.

But everyone knows it would be on very shaky ground as Sinn Fein is a growing force in the politics of Northern Ireland.

If the whole assembly is suspended, what does it mean for the peace process ?

The government would hope that over time it might rebuild trust, address areas of the Good Friday Agreement which individual parties are unhappy with and lay the groundwork for a return to devolution.

However the fear will be that, as in the past, a vacuum on the local political scene could be filled by the men of violence.

On a more day-to-day level, British ministers will take over the running of Northern Ireland government departments and some of the more bold initiatives of the devolved administration - such as a package to build much needed schools, roads and hospitals - could be put on ice.