A leading devolution expert has warned that Commons Leader William Hague's controversial push for "English votes for English laws" (Evel) could lead to Scottish independence.

Professor Jim Gallagher, who played a key role in the creation of the Scottish Parliament, criticised the former Conservative leader saying that his comments on the issue could threaten the Union.

Mr Hague came under fire last month when he appeared to suggest a link between extra powers for Holyrood and restricting Scots MPs' voting rights.

Downing Street later moved to insist that the two were not connected.

David Cameron faced accusations of betrayal after he announced the 'English votes' issue less than an hour after the independence referendum result.

Critics pointed out that the plan was not mentioned in the "vow" to Scots signed by the Prime Minister before polling day.

No 10 insists that the current system is unfair, as Scottish MPs can vote on issues that do not directly affect their constituents.

Opponents, however, argue that few Bills are genuinely "England only" with no repercussion for other parts of the UK.

England's size also creates huge knock-on effects on policies in Scotland, Wales and Northern Ireland, they warn.

Giving evidence to MPs, Prof Gallagher, from Oxford University, said that his view was that the issue of 'English votes' had to be tackled.

The former senior civil servant told the Commons Political and Constitutional Reform Committee that the lack of a national assembly meant that Westminster was "England's parliament" as well as the UK's.

But he added that any changes would have to be "consistent with the Union."

"And some of the things that Mr Hague has had to say suggest that it might not be." he added.

Prof Gallagher, who acted as an adviser to the Better Together campaign during the referendum, also said that giving English MPs a voice on English issues did not necessarily mean giving them a veto.

He has recently called for a "minister for the Union" to manage devolved relationships.

A No 10 source said that there was no link between the Smith Commission, which is currently looking at what extra powers to give MSPs in the wake of the referendum, and Mr Hague's cabinet committee, which the Prime Minister has tasked with looking at the issue of English laws.

l The Chancellor George Osborne will reportedly propose handing a range of new powers to major cities next month.

The Tory cabinet minister wants to boost a series of urban centres in his proposed "northern powerhouse."

However, it is thought that Mr Osborne will be reluctant to go as far as devolving significant tax-raising powers, as in Scotland.

Instead, he could offer them a much greater say over science, skills, schools and housing in their areas.