David Cameron is accounting for his decision to use Britain's veto at last week's European summit to MPs today.
The prime minister refused to participate in a Franco-German-proposed shift towards greater fiscal integration among EU members, after he failed to win safeguards for the City of London.
That decision has left opposition figures claiming Britain facing a new era on the fringes of Europe, as it now appears all 26 other EU states will press ahead with the measures through a separate intergovernmental treaty.
After the weekend saw Nick Clegg declare open warfare over the decision, the stage is set for another divisive coalition debate on the floor of the Commons this afternoon.
Ministers are doing all they can to prevent the row from escalating further, but Tory eurosceptics and frustrated Lib Dems are already at loggerheads.