Coalition in-fighting over voting reform has erupted at a Cabinet meeting when a Liberal Democrat minister directly confronted the Prime Minister over alleged dirty tricks.
With Thursday's referendum on changing the way MPs are elected fast approaching, Energy Secretary Chris Huhne aired his grievances at the weekly meeting of the Government's top team.
Lib Dem sources insisted it was an appropriate forum in which to raise "the lies and rather disgraceful behaviour" of opponents of a change to the Alternative Vote (AV) system.
But the minister found himself under fire from his own side - with the Yes to Fairer Votes campaign accusing him of obscuring the issues by engaging in political spats.
"Nothing Chris Huhne has done in the last few weeks was authorised by us or useful to us.
"The difficulty from day one was that we didn't want the referendum to be seen through the prism of the coalition," a source said.
Downing Street confirmed that Mr Huhne, who has threatened legal action against Tory cabinet colleagues, raised the issue at a point of the meeting reserved for parliamentary business.
He is reported however to have been rebuffed by Chancellor George Osborne - one of the main objects of his ire - who told him it was not an appropriate matter to discuss at Cabinet.
"If a private meeting with both sides is not an appropriate place to discuss the lies and rather disgraceful behaviour in these leaflets then I do not know what is," a senior Lib Dem source said.
The campaign on whether to replace the first-past-the-post system for electing MPs with the alternative vote has been marked by brutal exchanges between the coalition partners.