According to some forecasts, it could sky-rocket to nearly £5,400 in January, and even as high as £7,200 in April, which would plunge millions more into fuel poverty.
Speaking on the BBC, Mr Lewis said: “I am seeing such terrible panic out there from people, saying, ‘How will I be able to afford my bills?’
“You have Ofgem calling for more intervention, you have businesses calling for more intervention, you have energy trade bodies calling for more intervention, you have consumer groups calling for more public intervention.
“I am begging and praying and pleading that there is more Government help this winter … this is not catastrophising, it is a catastrophe that people will not die because of this, this winter.”
An emotional Mr Lewis called on the Government and the two candidates to pledge more support, saying help for the most vulnerable was “thousands of pounds short” of where it needed to be.
The Joseph Rowntree Foundation, a charity which works to combat poverty, said on current projections, said that single parents would be forced to hand over as much as two-thirds of their income after housing to energy bills, while some single adults’ energy bills would make up almost 120% of their income after housing costs.
It warned that some households would have to use their entire income to pay their energy bills and still have to find extra cash on top, meaning they would “almost certainly” become destitute as a result unless there is significant Government intervention.
The charity’s chief analyst, Peter Matejic, said: “In all my years as an analyst, I haven’t double-checked a piece of analysis as much as this one because it is so staggering, it feels incorrect.”
Speaking after the price cap announcement, Chancellor Nadhim Zahawi said officials were working “flat out” to develop more options to support households.
“This will mean the incoming Prime Minister can hit the ground running and deliver support to those who need it most, as soon as possible,” he added.
Boris Johnson, who will be replaced as Prime Minister when a new Tory leader is announced on September 5, said that current measures would be “increased by extra cash that the government is plainly going to be announcing in September”.