Sajid Javid warns Boris Johnson against spending splurge after shock resignation and takes swipe at Dominic Cummings

Sajid Javid has warned Boris Johnson not to go on a spending splurge in next month’s Budget, as he took a swipe at Dominic Cummings’ role in his shock resignation.

In a Commons statement, the former chancellor said the “critical” rules he drew up – to balance the budget and reduce debt – must not be abandoned, or taxes raised.

“It would not be right to pass the bill for our day-to-day consumption to our children and grandchildren,” Mr Javid said.

He insisted he still supported the prime minister, but joked about the “Cummings and goings” that triggered his departure two weeks ago – a clear reference to the role of the controversial chief aide.

And he issued a warning if the Treasury was no longer part of “checks and balances” on No 10, after Mr Johnson imposed a joint unit of advisers on his successor, Rishi Sunak.

“A chancellor has to be able to give candid advice to a prime minister so he is speaking truth to power,” Mr Javid said, in front of a visibly uncomfortable Mr Johnson.

He walked out after refusing to sack his advisers and amid rising tensions over spending plans and Mr Javid jumping the gun with his backing for the HS2 project.

It threw the government into chaos, threatening to delay the Budget on 11 March, which is intended to chart the course for a five-year government.

Mr Javid said the demand made on him “would not have been in the national interest”, adding: “These were conditions that I could not accept in good conscience.

He said: “I don’t intend to dwell further on all the details and the personalities.... the Cummings and goings if you will.”

And he told the watching prime minister: “I very much hope that the new chancellor will be given space to do his job without fear or favour.”

John McDonnell, Labour’s shadow chancellor, seized on the comments to warn that “choppy waters are ahead for Rishi Sunak and Boris Johnson”.

“Sajid Javid’s statement is not only a damning attack on Dominic Cummings’ dominance of the Johnson administration, but also an unashamed leadership bid to the group of Thatcherite backbenchers committed to resisting tax rises for the wealthiest and big business,” he said.

Backbench Tory opposition is believed to have seen off floated plans to raise money by squeezing pension tax relief for top-earners, abandoning fuel tax cuts, or through higher taxes on big homes.

It leaves the new chancellor wrestling with whether to scrap fiscal rules from the Conservative manifesto just two months ago, including to balance the day-to-day spending budget over three years.

Mr Johnson and Mr Cummings are both desperate to open the spending taps, to meet pledges made to voters who deserted Labour in the North and Midlands on election day.

But Mr Javid said: “These rules crystallise the choices that are required: to keep spending under control, to keep taxes low, to root out waste and to pass the litmus test, rightly set in stone in our manifesto, of debt being lower at the end of the parliament.”