Harriet Harman has urged the Government to back down on its plans for English votes for English laws (Evel) amid suggestions David Cameron could be headed for an embarrassing Commons defeat.

The interim Labour leader said Mr Cameron's English Manifesto at May's elections promised wide consultations, including with the Commons procedure committee, before changes went ahead.

But with only a week until the crunch Commons vote on the issue, Ms Harman said the committee had not yet been formed.

Several senior Tories raised worries about how the Government was carrying out its plans during an emergency debate yesterday. With coordinated opposition from Labour and the SNP, a handful of rebels could inflict Mr Cameron's first defeat as a majority Tory Prime Minister.

Speaking at Prime Minister's Questions, Ms Harman said: "In the English manifesto the Conservative Party published, you promised that before making changes to the constitution on Evel, that you would 'consult the House of Commons procedure committee prior to seeking approval from the whole House to the proposed standing order changes'.

"When did you do this?"

Mr Cameron replied: "There have been consultations with the head of that committee and there is plenty of time.

"I have to say to Labour, at least we published an English manifesto. I think it is a very simple choice for this House and for once, why don't we talk about the substance rather than the process.

"It's very simple: post devolution, we have a problem of unfairness which is English MPs have no say on Scottish issues and yet Scottish MPs have a say on English issues. That is the problem.

"We are proposing a very simple measure which is legislation shouldn't be passed on English matters against the will of English MPs.

"Are you really saying the Labour Party is going to oppose that proposal?"

Ms Harman said: "We agree there is a problem and we agree there needs to be changed.

"But it has got to be done properly, constitutional change has got to be done properly. You said at last week's Prime Minister's Questions 'we will publish our proposals shortly and Parliament will have plenty of time to consider and vote on them'.

"You can't have consulted the procedure committee because it hasn't even been set up yet. You should recognise the strength of feeling I think there is about proper processes to get to this change, strength of feeling on all sides of this House.

"I think you should consult properly or actually you are breaking a promise you made in your manifesto."

Mr Cameron ended the session by adding: "We have published proposals, we are having a debate in Parliament and there will be a vote in Parliament.

"I think the Labour Party frankly has got to get off the fence and tell us do you support this modest proposal or not? We are still waiting for an answer."