Spending pledges by the UK's two biggest parties are not deliverable, according to the Institute for Fiscal Studies.

Director Paul Johnson, speaking at the Fraser of Allander Institute's launch of the annual Scotland's Budget Report, suggested some of their announcements are simply "campaign rhetoric" .

It comes after the Conservatives accused the Labour party of looking to spend more than £1trn over the course of the next parliament if they get into power - a figure Labour refutes as "fake news".

Mr Johnson said: "In September in the spending round, the Conservatives promised some fairly significant increases in spending next year, particularly in health, education and social care.

"Obviously not undoing the cuts across the piste in the last decade or so. They're just about consistent with keeping the public finances under control.

"We've got Labour and the Conservatives proposing significant spending increases - they're just not deliverable.

"You can't double investment spending within three or four years in any sensible way.

"We wait to see what their broader spending plans are going to be."

The economist also said more promises are likely to be made in the next five weeks as the December 12 poll date approaches.

Asked if he thinks some of the spending pledges are "campaign rhetoric", Mr Johnson said: "I think there's a lot of that already.

"The Conservatives have suggested that Labour have £1trn in spending pledges - that's clearly not the right number but it reflects all sorts of promises or suggestions or indications that Labour have made of things they'd like to do.

"Of course, the Conservatives are doing the same thing, just like they did at the last election about more GPs and more GP appointments, which sound good - but where's the money coming from?"