At a major press conference detailing a climb down on climate change targets yesterday, Sunak was asked directly to comment on rumours that HS2, due to run on zero carbon electricity, could be scrapped to fund future tax cuts.

Sunak said: “I’m not going to speculate on all the other things that people will be taking about.

“I am focused today on finding a fair and proportionate to deliver net zero.”

Civil engineers reacted with alarm to the report at the end of last week that the Prime Minister and Chancellor Jeremy Hunt are looking to scrap the project’s northern leg in a bid to save £35bn

They warned the move would be short-sighted and undermine the UK net zero goals for 2050.

Civil Engineering Contractors Association chief executive Alasdair Reisner said: “Cancellation of such a nationally-significant project will level down rather than level up, massively undermining the ability of the UK economy as a whole to grow, and threaten delivery of Net Zero by 2050.

“In simple terms, a decision to axe the northern sections of HS2 would mean that we are unlikely to see high speed rail in the North anytime in the first half of this century.”

A spokesperson for the High Speed Rail Group said: “The backlash around the Government’s indecision on HS2 is inevitable given the impact any cancellation will have upon the 30,000 people working on the project, as well as on the millions of people across the North and the Midlands.

“The Government needs to kill the speculation and make its intentions clear.

“We urge the Government to continue to listen to people in the North and the Midlands who deserve the widespread economic benefits this project is already delivering and commit to it being delivered in full.

“Recent polling by YouGov shows support for the project halves without building the line to Manchester.

“The North and Midlands deserve this project. Our national and regional economies deserve this project.”