Scots should have another referendum to keep them in the Union, a leading expert has suggested.

The vote would "endorse" the new powers going to Holyrood, according to John Curtice, professor of politics at Strathclyde University.

Without such backing from the public Unionists politicians were always going to be in a difficult position, he said.

His comments came as he gave evidence to the House of Lords Constitution committee.

Asked how Scotland could be kept in the Union, he told peers: “I think you should be holding a referendum on the provisions of the Scotland Bill going through this place.”

The vote would force ”the public to engage on the issue,” he said.

He added: “The truth is that it is perfectly clear simply having held a referendum and having 55 per cent in favour of staying inside the UK has not done anything nothing to quell the debate.

“ If you want to try and cement Scotland’s place in the Union then the Unionist side has to stop apparently running away from facing the public and be willing take what you want to do and get a positive endorsement.”

He went on: “If you get a situation with a majority voting for this then you can say not only did people vote against independence but people actually voted for this, this is what people in Scotland actually wanted.

In the absence of that kind of endorsement you are always going to be in a difficult position.”