Boris Johnson is considering ripping up Sajid Javid’s fiscal rules to allow for more spending and tax cuts to boost the economy after Brexit.

No 10 signalled on Friday that the spending rules set out in the Conservatives’ general election manifesto could be loosened as the Prime Minister attempts to lift the economy.

It came amid speculation that Rishi Sunak, the new Chancellor, will back Mr Johnson on VAT reform and investing in free ports. The Government this week began a consultation on the economic zones, which runs until April.

The Budget may include stamp duty cuts for main homes, which Mr Johnson supports, and cuts to high street business rates.

The Tory manifesto committed the party to fund day-to-day spending without borrowing, although it did not set a time frame for the pledge.

The Government is planning to spend an extra £20 billion a year on investment, but a looser definition – such as “investing” in teachers’ salaries – could allow current spending to rise.

Pressed repeatedly over whether Mr Sunak would stick to these rules, a No 10 spokesman only said that they would be confirmed at the Budget next month.

“We will continue to have a clear fiscal framework,” the spokesman said. “The Chancellor is busy getting down to work and that will continue through the weekend as preparations for the Budget continue at pace.”

A senior Downing Street source later refused to say the fiscal rules remained unchanged, adding: “We were elected on our manifesto, we are going to deliver our manifesto and the PM is committed to his manifesto.”