The Government was maintaining a discreet and cautious silence tonight following Ulster Unionist leader David Trimble's failure to secure re-election as Northern Ireland's first ministers.
Officials said the position at Stormont was being assessed ahead of any comment on developments.
But Labour party leader Ruairi Quinn said the move marked "a most serious setback for all who hoped that Northern Ireland was poised to enter a new period of political progress, which would allow the full implementation of the Good Friday agreement."
He added: "It is a particular disappointment, coming so soon after the historic decision of the IRA to commence the process of decommissioning."
Mr Quinn claimed those Ulster Unionists who voted against Mr Trimble had put their own sectional and political considerations ahead of the interests of the broad community - and jeopardised all the progress made since the Belfast Agreement.
"Having made decommissioning their main demand since 1998, the DUP and the anti-agreement UUP members, are exposed as hypocrites following their vote today."
The Labour leader said the British and Irish governments had now to consider all the options open to them - a process that could require a period of consultation and dialogue.
"Every option, consistent with the core principles of the Good Friday agreement, should now be considered to allow the re-establishment of all the institutions and the full implementation of the agreement."
PA