A UK government minister on Sunday said it would be "irresponsible" to keep ploughing money into a new high-speed train line if there has been a change to the country's "fiscal picture".

Defence Secretary Grant Shapps was speaking after a string of reports said Prime Minister Rishi Sunak was considering scrapping the colossal HS2 rail project which has seen costs spiral.

The UK is currently in the grip of a cost of living crisis that has seen housing and food costs hiked, prompting a wave of crippling strikes across the economy from doctors to train drivers.

The country's defence budget is also under pressure faced with a range of new challenges including the war in Ukraine.

"There are various different estimates and I think that's one of the things that the government wants to check, particularly on the costs now post the inflationary picture out of the war in Ukraine," Shapps told BBC television.

"I have to say that it would be irresponsible to simply spend the money, carry on as if nothing had changed, if there has been a change in that fiscal picture," he added.

Designed to bring the major cities in the north of England closer to London, the HS2 project was estimated at £37.5 billion ($46 billion) in 2013, but has since soared to around £100 billion.

It will be Britain's second high-speed line after HS1 -- used by Eurostar in southeast England.

Shapps, a former transport secretary, told Sky News a decision would be taken "in due course".

But if costs kept increasing "there has to be a point at which you say 'hold on a minute, let's just take a break here'", he said.

A general election is expected next year with Sunak's Conservative Party currently trailing the main opposition Labour Party in polls.