At meetings between Mr Blair and Labour backbenchers last week, MPs accused Mr Mackay of "winding up" Ulster Unionists who opposed the Good Friday Agreement. They said this had made it harder for David Trimble, the party leader, to win support for the devolution proposals which the Unionists rejected earlier this month.
The Prime Minister backed the MPs' complaints. "The Tories have always played games over Northern Ireland," he said. "Look at the history books. They just want to make trouble for the Government."
Mr Blair is said to be furious that the Tories backed Ulster Unionist attempts to amend the emergency legislation on the devolution plans, despite Mr Hague insisting the Opposition maintains its bipartisan approach to the peace process.
Other Cabinet ministers attacked Mr Hague's approach in talks with Labour backbenchers. Frank Dobson, the Health Secretary, said: "We must make the Tories pay for this in the long run."
Mo Mowlam, the Northern Ireland Secretary, endorsed comments by Peter Temple-Morris, the former Tory MP for Leominster who defected to Labour, that the Tories had "behaved disgracefully". Butshe said ministers were inhibited from going public on such criticism.
One Labour MP in the talks said there was no doubt the "frustration and anger" at the Tories' position extended from the backbenches to the top of the Government.
The Tories deny undermining Mr Blair's efforts, saying the Opposition was within its rights to improve the proposed legislation. They insist the cross-party approach to Northern Ireland is still intact.
The prospects of an early kickstart to the stalled peace process looked gloomy last night after Patrick Doherty, the Sinn Fein vice-president, dismissed the idea that the IRA could decommission its weapons by next May, as set out in the Good Friday Agreement.
He said: "I think it's entirely out of the question given the context that the Unionists have walked through every deadline that was set, either in terms of the Good Friday Agreement or those deadlines set by both [British and Irish] governments."
On BBC1's Breakfast with Frost, Mr Doherty claimed the British Government had "aided and abetted" Unionists in refusing to create a political context which would pave the way for decommissioning. "That is the crisis," he said.
Mr Doherty said the onus was on the British government to see that the Unionists did not continue to block progress.Reuse content