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Boris Johnson has been forced to defend his ever-growing list of uncosted spending commitments.

The Tory leadership hopeful even said he is willing to see borrowing go up if it was "to finance great infrastructure projects".

It marks a radical break from the austerity politics forced on British public services by Mr Johnson's party for almost a decade.

In an interview with Sky News, the Tory leadership hopeful said there is "cash available" to deliver his raft of promises - including a tax cut for the wealthiest.

Last week Mr Johnson unveiled a plan to put an extra £4.6bn a year into schools by 2022-23.

Asked by Sophy Ridge how he intended to pay for promises - which include a tax cut, a vow to put more police on the streets and a plan to raise spending on schools - Mr Johnson defended his commitments.

Mr Johnson said: "I think education is the single most important thing that we Conservatives believe in.

"In the sense that it is the tool that every kid should have to make the most of their talents and their opportunities, and a great education is the job of the state to provide to absolutely everybody.

"So what I want to do, day one is level up and make sure that everybody, primary schools and secondary schools, get the funding they need."

Mr Johnson insisted there was "headroom available" in the public finances and said his "sensible tax cuts" would generate growth and so increase revenue.

He said: "Well actually, of course, as the great Tunisian scholar and sage Ibn Khaldun pointed out as early as the 14th century, there are plenty of taxes that you can cut which will actually increase your revenues and there are ways of making sure that you stimulate growth, you stimulate enterprise and you get more in.

"But what is certainly true is at the moment there is cash available."

He added: "I think at the moment there is the headroom available and we intend to use it.

"I also think you can do some great things to stimulate economic growth with tax cuts."

He told Ms Ridge: "There is headroom of about £22-25 billion every month.... At the moment there is headroom available and we intend to use it."

He added: "I'm prepared to borrow to finance certain great objectives but overall we will keep fiscal responsibility and keep going with the objective of making sure this country pays its way and lives within its means."

But last week The Institute for Fiscal Studies found that the top 10% of earners would gain an average of nearly £2,500 a year under Mr Johnson's plans.

Mr Johnson has said he will increase the income tax higher rate threshold from £50,000 to £80,000 becomes PM.