Ms Reeves denied the freeze in the tax thresholds was a breach of the manifesto because it “referred to the rates of income tax and National Insurance and the rate of VAT”.

The run-up to the Budget was marked by multiple leaks about the Treasury’s plans. This culminated with the Office for Budget Responsibility (OBR) publishing its assessment online before the Chancellor had delivered her speech.

Treasury permanent secretary James Bowler told the MPs a leak inquiry will cover ministers as well as officials and advisers.

Ms Reeves said: “The Budget had too much speculation. There were too many leaks, and much of that, those leaks and speculation, were inaccurate, very damaging, as well as the IT security issues.

“I want to say on the record how frustrated I am and have been by these incidents and the volume of speculation and leaks, and that is why I am doing something about it, because we cannot allow this to happen again.

“A leak inquiry is under way with my full support, being led by the permanent secretary at the Treasury, and we are also conducting a review of the Treasury security processes to inform future fiscal events.”

Ms Reeves insisted a Financial Times story that disclosed she had dropped plans for an income tax rise was based on a leak, not an authorised briefing.

Describing the story as “incredibly damaging”, she told the MPs: “It was not briefing that was signed off by me, any of my ministers or officials. It was unacceptable. That is why there is a leak inquiry going on.”

Mr Bowler hit back at the suggestion leak inquiries “don’t get anywhere,” saying: “It is the case that, even in the last year, across government, civil servants have been found to accidentally or deliberately leak information and that has led to action including dismissal.”

During the Treasury Committee hearing, the Chancellor clashed with former Treasury minister Dame Harriet Baldwin.

Dame Harriet said: “In the run-up to the General Election you said that you had no plans for tax rises beyond what was in your manifesto and that you would focus on growth.

“You have now put together two of the biggest tax-raising Budgets in UK history, and the Office for Budget Responsibility has told us that there is not a single measure overall that has a positive growth impact.

“They think, in fact, tax hikes are harming growth.”