The government has been accused of hastening Scottish independence after it unveiled plans to give English MPs a veto over laws affecting England.
David Cameron's English votes for English Laws (Evel) proposal was branded a cynical attempt to artificially inflate the prime minister's slim Tory majority and even "racist".
Today the leader of the Commons, Chris Grayling, was heckled by SNP MPs as he set out the measures that he said finally answered the infamous West Lothian question.
"It’s really important everyone feels our constitutional arrangements are fair, so this one nation government will end the anomaly that a majority of English MPs can be outvoted on matters which are devolved elsewhere," he said.
"At a time when we’re giving more power to the Scottish Parliament and the Welsh Assembly, it’s right the English should have a veto over things that only affect their constituents."
The constitutional change will be made by amending the standing orders of the Commons rather than introducing legislation. Under the proposals the Speaker will be asked to determine whether a Bill will be subject to the new Evel rules.
If the Speaker decides a Bill is entirely English-only in its impact, it will be subject to scrutiny by a new English-only committee stage in the Commons before continuing along the normal route through parliament.
If the House of Lords amends Bills that have been certified as England only, those amendments will be subject to a double majority vote. This means amendments will have to be supported by a majority of English MPs well as a majority of all MPs before they can become law.
Labour's shadow leader of the House, Angela Eagle, agreed English MPs needed to be given a greater voice over English matters, but slammed the "rushed and partisan" way it was being introduced. "This is no way to make profound constitutional change," she said.
And she warned the double majority idea risked creating "two classes of MPs" in the Commons for the first time. "These proposals risk the union rather than saving it," she warned. "The leader of the House is playing with fire why is he being so reckless."
Eagle, who is running to be Labour's deputy leader, added that it was a "a cynical attempt by a government with an overall majority of just 12 to use procedural trickery to manufacture itself a very much larger one".
Grayling faced a wall of noise from Scottish National Party MPs as he read out the new proposals. And the SNP's Pete Wishart furiously denounced Evel as "constitutional bilge" and "unworkable garbage".
He said the plan would make movement towards Scottish independence "even more irresistible". Wishart added: "By God, this lot are going their best that Scotland becomes an independent nation. I almost congratulate them."
Labour backbencher Gerald Kaufman, who as the longest serving MP is the father of the House, also savaged the plan. "Even the title of this motion sounds racist," he said.
"Is it not a glory of this house that every MP from those holding the highest office through to the most newly elected MP is equal in the division lobbies. Is it not a fact that this government is undermining not simply whatever differences there may be between outlooks from people of different counties within the UK but this government is undermining the whole basis of British democracy," he added.
The government has dismissed SNP and Labour complaints that introducing the changes by amending the standing orders rather than introducing legislation is wrong. A government source said: “When you change rules, it’s the way the Commons operates. You have to it by standing orders. This is how you do it this. There is no other way to do it. It is totally appropriate.”