Kenneth Clarke wants English MPs voting on English matters

A party spokesman said the Tories were "almost certain" to back the idea, which has been recommended by a task force led by Kenneth Clarke.

The debate over the post-devolution role for Scottish MPs became known as the "West Lothian question" after being first posed by former MP Tam Dalyell.

Tory leader David Cameron supported the idea in his party's leadership contest.

The measure was also included in the Conservative manifesto at the last election.

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The Tories want to end what they believe is the unfairness of Scottish MPs voting on issues such as health and education in England, although these matters are decided by the Scottish parliament north of the border.

That could dent the leadership credentials of Gordon Brown, who represents a Scottish constituency.

The Conservatives are planning to raise the issue in a debate later this month, but the government is strongly resisting their plans.

Mr Clarke told the Observer newspaper: "If a man landed from Mars and saw the current system, he would not say that democracy was working properly."

Conservative MP Alan Duncan told the BBC it was "absolutely right" to stop MPs voting on issues which did not affect their constituents because they were now decided by the Scottish Parliament.

"I'm beginning to think it is almost impossible now to have a Scottish prime minister because they would be at odds with the basic construction of the British constitution," he said.

"We have MPs from Scotland essentially telling England what to do when they are doing the opposite in Scotland, have no control over what they are doing in their own constituencies in Scotland and are not in any way accountable for the effects their actions have in England."

Two-tier system

Trade and Industry Secretary Alistair Darling spoke out against the Tory plan - saying it would introduce a two-tier system.

"I have always said that there is a huge problem of having two classes of MPs at Westminster," he told the Observer.

"I am a member of this government, I am collectively responsible for everything they do and it would be very odd if you said, well I can't vote for it."

Liberal Democrat Sir Menzies Campbell, MP for North East Fife, warned against any "knee-jerk response" to the issue.

"A constitution is like a brick wall - if you take out one brick without regard to the strength of the wall, it all comes tumbling down.

"What we need is a Constitutional Convention to provide a constitution for 21st Century Britain.