Prime Minister Andy Burnham told BBC Radio 4’s Today programme he would not call Rossi’s crisis warning an overstatement, adding that the cost of home energy, as well as petrol and diesel, was “very difficult indeed”.

Speaking from the Labour conference in Liverpool, he added: “We’re looking at any measure that can give people breathing space, that can take the pressure off.”

About 20 million households in England, Scotland and Wales are on variable energy tariffs set by Ofgem’s price cap, which puts a maximum price on each unit of gas and electricity.

Those homes will see a 4% increase in prices on Thursday, the equivalent of about £60 per year – or £5 per month – taking an annual bill to £1,723 for the typical household using both electricity and gas and paying by direct debit if this level was sustained for a year.

That rise would have been higher without the government’s VAT cut, which knocks the equivalent of about £45 a year off a typical bill.

But forecasts show a far greater increase is possible for bills in January. Cornwall Insight said its latest forecast suggests the typical annual bill would rise to £1,999.