A new poll by YouGov has found that the 'No' vote in the Scottish referendum now has a marginal lead.

The poll of 1,300 people on the issue of Scottish independence for The Sun and The Times was taken over Tuesday to Thursday.

It covered a period when the leaders of the three main parties all visited Scotland and former Prime Minister Gordon Brown stepped up his involvement in the drive to keep the union.

The Yes campaign, led by Scotland's First Minister Alex Salmond, had been buoyed at the weekend with one YouGov poll putting it marginally ahead of former Chancellor Alistair Darling's Better Together.

There had been fears that a poor performance by David Cameron, Ed Miliband and Nick Clegg, who all travelled north of the border on Wednesday, could result in Yes gaining further ground.

The former premier spoke to Sky News on Sunday and made a speech on Monday setting out an alternative timetable to give the Scottish Parliament more control over finance, welfare and taxation, in the event of a No vote.

A poll released on Thursday, by Survation, found 53% were expected to vote No, and 47% yes. This was unchanged from August 28.