Government sources believe it is increasingly likely that Mr Sunak will need to raise the threshold at which National Insurance Contributions (NICs) are paid in order to counter some of the effects of the NICs increase due to take effect next month.

Ministers are split over how to respond to the crisis and, this weekend, senior Tories descended into open criticism of each other over the Government’s approach to the 2050 net zero target. 

Lord Goldsmith, the environment minister, ridiculed Oliver Dowden after the Conservative chairman and Cabinet minister warned that the public wanted to see “less net zero dogma” and endorsed the Prime Minister’s nuclear ambitions.

Last year, Lord Goldsmith warned that nuclear was “the most expensive form of energy in the history of energy” – a criticism that Mr Johnson appeared to tackle head on last week. In an article for The Telegraph, the Prime Minister said: “So now is the time to make a series of big new bets on nuclear power. The 1997 Labour manifesto said there was ‘no economic case’ for more nuclear – even though nuclear is in fact safe, clean and reliable.

“It is time to reverse that historic mistake, with a strategy that includes small modular reactors as well as the larger power stations. It was the UK that first split the atom. It was the UK that had the world’s first civilian nuclear power plant. It is time we recovered our lead.”

On March 7, Mr Johnson said he would set out an energy supply strategy “in the days ahead” after Russia’s invasion of Ukraine pushed oil and gas prices to multi-year highs.

One government source suggested that Mr Sunak’s resistance to the Prime Minister’s nuclear plans was a significant factor behind the delay publishing the strategy – a claim denied by another source. The strategy is due to be published at the end of this week, or early next week. 

Defending Mr Sunak, one government source said that Mr Johnson’s plans amounted to “high level ambitions”, adding: “Obviously you can’t sign off funding for a policy when you don’t have the detail of how it’s going to work yet.”

The Nuclear Energy (Financing) Bill currently going through Parliament sets out a funding model to incentivise private investment in new plants. Currently, the Government is only committed to financing one new nuclear plant by the next election. Mr Johnson wants to go significantly further, as some MPs push for the equivalent of eight large plants by 2050. 

All but one of Britain’s existing nuclear reactors are due to be decommissioned by 2030.

In a speech to the Conservative spring conference in Blackpool on Saturday, Mr Johnson said that Britain “will make better use of our own naturally occurring hydrocarbons, rather than import them top dollar from abroad and put the money into Putin’s bank account.”