Tory leader David Cameron has been accused of threatening the break-up of the United Kingdom after the Tories unveiled proposals to strip Scottish MPs of the right to vote on English matters at Westminster.
Ministers rounded on the Conservatives, accusing them of "playing fast and loose" with the constitution amid growing tensions between London and Edinburgh.
Under the Tory proposals, a new English Grand Committee - open only to English MPs - would be established to deal with legislation, such as schools and hospitals, relating solely to England.
MPs from England, Scotland, Wales and Northern Ireland would continue to sit together in the Commons to vote on UK wide matters such as taxation, foreign policy and defence.
The plan is the brainchild of ex-Scottish Secretary Sir Malcolm Rifkind who drew up the scheme to address the perceived growing constitutional imbalance which has grown up since devolution to Scotland and Wales. A Tory party spokesman confirmed that the proposals were being considered by Mr Cameron's democracy taskforce, led by ex-chancellor Kenneth Clarke, but insisted that no decisions had been taken. However, with Mr Clarke due to deliver his final report before the end of the year, party chairman Caroline Spelman gave the proposals a warm welcome.
"I think it would give a sense of fairness and complete the devolutionary process," she said.
"Having English MPs voting on laws that only pertain in England would address that sense of unfairness that English MPs had when the Labour Government only got its way on tuition fees and foundation hospitals because Scottish MPs were able to vote on that, even though those laws would not apply in Scotland."
Labour deputy leader Harriet Harman warned that Sir Malcolm's proposals - first floated almost a decade ago in 1998 - threatened the unity of the United Kingdom. "I don't think it is right to break up the United Kingdom and I think that that's where ultimately the suggestion of the Conservatives would go," she said.