RUTH Davidson and David Mundell made an “astonishing” error in putting their names to a bungled Tory attack on Scottish Government spending, it was claimed last night.

The Scottish Secretary and Scottish Tory leader were accused of “voodoo maths” after claiming SNP policies meant an extra £1bn tax burden on Scots by 2021.

The Conservatives later admitted almost £400m of the extra money going to Holyrood was due to Tory income tax policy changing the annual block grant in Scotland’s favour.

Read more: Award-winning chippie dishes up suppers for king of Sweden

The row started after the Scottish Tories claimed an “analysis of SNP tax policies” showed a cumulative “Scotland surcharge” of £1.03bn by 2020-21 because of reforms to income tax, business rates, property taxes and air passenger duty.

Ms Davidson said it showed the SNP wanted to “clobber hardworking families and make Scotland the highest-taxed part of the UK”, while Mr Mundell said the SNP would “have to account to the Scottish people for their plan to tax Scotland £1bn more than England”.

But it emerged £378m arose from the Tory pledge to raise the threshold for the upper rate of income tax to £50,000 and the SNP not following suit, which boosts the block grant.

Scottish LibDem leader Willie Rennie said: “This is an embarrassing gaffe from David Mundell. The Tory figures are voodoo maths from a party desperate to divert attention from the chaos they unleashed with Brexit.”

Read more: Award-winning chippie dishes up suppers for king of Sweden

A Tory spokesman said: “The UK Government is reducing income tax so Scotland gets compensated by about £300m a year by 2020.

“The SNP choose not to pass it on, but pocket it. That's a stealth tax rise.

“It doesn't matter that it's coming from the block grant adjustment - by taking a different course to the UK, they are choosing to keep taxes higher by the equivalent of £1bn.”