Coalition talks over English votes for English laws have reached deadlock, Politics.co.uk can reveal.
Conservative negotiators led by leader of the House William Hague are refusing to accept Liberal Democrat proposals over the makeup of a new England-only 'grand committee' legislative stage.
The talks, which began earlier this week, are set to continue throughout next month, but agreement now seems unlikely.
Labour has refused to participate in the talks as Sadiq Khan focuses on a constitutional convention.
It means all three mainstream Westminster parties are now divided over English votes for English laws.
"The issue of treating England fairly cannot be avoided any longer," Hague said.
"Labour refuse even to discuss this, but Conservatives and Liberal Democrats are continuing our discussions. It is time to be fair to all parts of the United Kingdom."
The stakes are high for the Conservatives. If they are able to succeed in finding a way of cutting out Labour's Scottish votes it will become much harder for their opponents to pass reforms in England.
But both Labour and the Lib Dems are warning of a "stitch-up" and remain deeply suspicious.
"Holding meetings behind closed doors in Westminster, chaired by a former leader of the Tory party, smacks of a Westminster stitch-up," a Labour party spokesperson said.
"This is not the best way to find a solution to very complex constitutional issues. That's why we want to see a constitutional convention get to grips with a number of interrelated issues, including how we find a solution to the English question."
Deputy prime minister Nick Clegg has also spoken out in favour of a constitutional convention dominated by the public rather than politicians.
"We are also determined to resolve English votes on English matters but this must not be a politically motivated stitch-up by the Tories," a Liberal Democrat spokesperson said.
"That is why the Liberal Democrats have proposed a grand committee system to allow English MPs, appointed proportionately, to vet laws that will apply only in England."
The Lib Dems say the balance of MPs on a grand committee, which would have around 80 members, should reflect each party's share of the popular vote rather than the number of seats they hold in the Commons.
They argue this is the right approach because PR is used to elect representatives to the assemblies which decide devolved matters in Scotland, Wales and Northern Ireland.
Labour would be the biggest losers of such a change, while the Tories claim it would cut their party's representation in a grand committee by around ten per cent.
Sources close to the leader of the House make clear PR is a red line the Conservatives will never accept. Voting reform was rejected by two-to-one in the 2011 electoral reform referendum, they point out.
Hague has made clear he will force a vote in the Commons if cross-party talks do not reach agreement by the end of November.
This will be a decisive moment. Right now, the worst-case scenario for the Tories is they make no further progress in the talks and are faced with an improvised Lib-Lab coalition.
If that were to happen, it's far from clear that the Conservatives would lose. They currently have 302 MPs, leaving them 19 short of a majority.
Not once has Labour managed to get all of its MPs to vote in the Commons in the same division in this parliament. The Tories have several times. If the SNP support the Conservatives, which is not out the question given they've indicated they support English devolution, it would only take six or seven Labour rebels for a decisive majority.
The Conservatives haven't yet revealed their hand and put forward their own proposal. Perhaps it might take the form of a double-majority system, in which English MPs are effectively given a veto. Under this idea reforms which only apply to England would not pass if a majority of English MPs opposed them.
This might just be the formula the Tories need to placate the English and win over just enough Labour MPs. If it is, Hague will have done more to secure his party's permanent dominance of English politics than David Cameron ever did.