Boris Johnson has faced a Scottish Tory backlash after it emerged his flagship leadership plan for income tax cuts in England would be partly funded by Scots paying hundreds of pounds more.

The former Foreign Secretary's proposal to increase the point at which people start paying the higher rate of income tax from £50,000 to £80,000 would not benefit Scots, as the levy is devolved to Holyrood.

But Mr Johnson intends to partly fund the £9.6 billion tax cut by increasing employee national insurance payments in tandem, a change that would apply across the UK.

This would widen the existing cross-Border tax gap, with Scots paying a total of 53p in the pound on any earnings between the Scottish higher rate income tax threshold of £43,430 and the new English figure of £80,000.

An analysis by the Chartered Institute of Taxation (CIOT) showed Scots earning £60,000 a year would see their national insurance bills rise by £1,000, while those earning £75,000 would pay £2,500 more.