Conservative ministers have privately written off any chance of getting a deal to restrict Scottish MPs voting rights before the next general election - amid opposition from the Liberal Democrats as well as Labour.
Senior Tory sources also indicated that they were happy that "English votes for English laws" would be a so-called wedge issue with other parties in 2015.
The Tories and Labour have been at war over the move since it was announced two weeks ago.
But yesterday a LibDem member of the cabinet committee set up to look into the English votes issue threw a potential spanner in the works.
David Laws suggested that the Tory plan could only work if it included proportional representation (PR), the electoral system hated by the Conservatives.
The Tories ran a ferocious campaign to kill the LibDems' referendum to introduce a form of PR in 2011.
But Mr Laws suggested that "English votes for English laws" could not go ahead without incorporating such a system.
He said that any "grand committee" of English MPs who could potentially veto English- only legislation would have to be chosen proportionally, by the votes each party got at the general election, not by the number of seats. And his views are echoed by LibDem leader Nick Clegg.
The cabinet committee has been set up under William Hague.
Publicly, the Conservatives are pressing Labour to sign up to the idea and feed into the committee's work. But senior party sources admit they do not expect to get any cross-party agreement - because of opposition from the Lib Dems as well as Labour.
One Tory minister said: "We do not expect to get a deal on English votes for English laws, not least because of opposition from the LibDems."
He added: "We have no problem going into the next election with this as a dividing line between us and the other parties".
Labour have accused Mr Cameron of trying to set up an English Parliament within the House of Commons that he can control even if he loses the keys to Downing Street next May. Some Labour MPs have even claimed Mr Cameron is guilty of attempted "gerrymandering" over the row.
Last night the SNP called on the main pro-Union parties not to let wrangles over the issue interfere with plans to devolve extra powers to Scotland.
But SNP Westminster leader Angus Robertson said: "The Vow the Westminster leaders made to the people of Scotland in the run-up to the referendum promised to deliver substantial and 'faster' new powers. In the event of a Yes vote, independence would have been delivered in 18 months. Three years for further powers is simply not good enough.
"English votes for English laws is nothing to do with what was promised to Scotland. The powers we need cannot be held to ransom.
"These new back-door terms that Westminster is trying to sneak in are totally unacceptable; the Westminster parties will pay a heavy price for any betrayal of the people of Scotland at the ballot box.
"It is time for the Scottish Parliament to have the powers we need to make Scotland a fairer, more equal country and address the causes of inequality. Mr Cameron made a promise to the Scottish people and he must now honour it."
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