DEREK Mackay has called on the Scottish Tories to block Boris Johnson’s controversial tax cut for the rich.

On Monday the former foreign secretary, who is the favourite in the race to replace Theresa May as Prime Minister, unveiled a new £9.6 billion tax cut for high earners.

Under Johnson’s plans, the 40p tax threshold would jump from £50,000 to £80,000, which would be partly funded from a hike in national insurance contributions.

READ MORE: Johnson reveals plan to make Scots fund tax cut for rich in England

But while income tax is devolved, national insurance is reserved – leaving Scots worried they would be funding the giveaway.

Though the IFS said yesterday that the fiscal framework agreement between the two governments means this would ultimately result in higher block grant funding for the Scottish Government, it would still put Mackay under immense pressure to use that money to follow suit.

The IFS also said the main beneficiaries of Johnson’s tax proposal will be pensioners on a high income who don’t pay national insurance. They will effectively see their marginal rate of taxation fall from 42% to 20%.

Though pensioners with a high incomes make up only a small percentage of the population, they make up nearly half of all the Tory members who will ultimately decide who becomes the party’s next leader.

Mackay (pictured below) said Johnson’s plans would undermine efforts to “make Scotland fairer and more prosperous”.

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He said: “After the last Westminster election the Scottish Tories made much of the idea that they would vote as a block in the House of Commons to protect Scotland’s interests – but there has been no evidence of this so far.

“They were silent when their bosses handed over £1bn to Northern Ireland to buy off the DUP – but they simply cannot remain silent in the face of this Boris tax.

Ruth Davidson must immediately make clear – does she support Boris Johnson’s tax hike? If she doesn’t, will she instruct all 13 of her MPs to vote against any UK Budget in which these outrageous tax plans are included?

The National:

“Or will she simply fall into line with the Tory leadership and forget about her previous statements, as she so often does?”

A spokesman for the Scottish Tories said: “The SNP should worry about its own tax agenda, which punishes thousands of Scots, before looking at anyone else.”

The first ballot in the Tory leadership race will be tomorrow. Any of the 10 contenders who fails to win the support of at least 16 of their MP colleagues will be eliminated from the contest.

Johnson, who is expected to launch his campaign today, found himself accused of “not having the guts to face the people” after he refused to confirm his participation in a BBC debate.

Rival in the race Matt Hancock said: “I certainly think that everybody who puts their name forward to be prime minister should be open to scrutiny, should be accountable.

“Everybody should participate in the proposed TV debates. And I think we’ve got to ask the question: why not? I’ve got nothing to hide and that’s why I am here.”

Harper, one of the outsiders, said contenders needed to be prepared to open themselves up to questioning.

He told journalists to ask him anything, and then answered questions, on issues including immigration and Brexit, for over an hour and a quarter.

The last question came from a Daily Mirror reporter who asked the Tory who he thought would win in a fight between a bear and a lion.

The former chief whip said: “Because the lion is a symbol of Britain, I’ll go with the lion.”