Consumer champion Martin Lewis has warned people will die as they are forced to choose either heating or eating when energy bills rocket.
He added Britain faces an “absolute poverty crisis” and called for action to shield millions from soaring costs.
The Money Saving Expert said a “substantial” hike in funds was needed to help those most severely hit by the prices surge.
He told the BBC : “We are going to have to put money into the system or we are going to have an absolute poverty crisis, with people being unable to eat or dying because of the cold.”
His message came as Ofgem is due to unveil the price cap hike for 15 million families on February 7.
Last week it was predicted the limit for 11 million on standard or default tariffs would leap by 50% – 10 times the rate of inflation.
Costs might rise from £1,277 to £1,925 from April 1, an extra £648 a year. Consultants Cornwall Insight said the average bills could surge beyond £2,000 next winter.
A cap for four million with prepayment meters, often among the poorest, is also set to soar.
Pressure is piling on Chancellor Rishi Sunak to offset the hikes.
Mr Lewis said axing the 5% VAT on energy costs, a Mirror-backed move that could shave £100 off bills, was one option.
He called for a targeted version of the cap to freeze bills for vulnerable families.
Mr Lewis urged widening the criteria for the £140 Warm Homes Discount to include those eligible for Universal Credit.
He also hit out at the market which has rewarded those who have shopped around for cheap deals. It came as a report warned millions of families in England will fall into fuel poverty overnight.
Think-tank the Resolution Foundation predicted households who will find energy unaffordable will treble to 6.3 million.
Meanwhile, Dermot Nolan, the former head of Ofgem, said the crisis caused by soaring wholesale gas prices was a “worldwide phenomenon”.
But the regulator has been slammed for failing to tackle problems unique to the UK.
They include criticism over dozens of suppliers that have gone bust due to the costs surge, leaving households to pick up the huge bill.
Mr Nolan said: “We have got a number of things wrong but fundamentally it is not our fault that gas prices have risen internationally.”
Sunak 'missing in action'
While Chancellor Rishi Sunak has been labelled “missing in action”, European governments are already limiting the impact of soaring energy prices.
The French government last week announced plans to cap the rise in energy bills to 4%.
The forecast here is 50%.
It comes through EDF being forced to sell electricity generated by its nuclear reactors to rival home suppliers at well below market prices, now at a record high.
Italy has vowed to come down hard on firms selling energy at “crazy margins”. Enel, the energy group part-owned by the state, said last week that it would be selling all its electricity at non-inflated prices.
While Sunak, below, snoozes, in Germany the government has cut a surcharge on bills used to support renewable energy schemes.
Here, Labour wants a windfall tax on North Sea oil and gas producers, to fund a £200 cut in the average home energy bill.
Fossil fuel companies would have to contribute £1.2billion to help fund the plans, via a year-long increase to their corporation tax of 10%.
It comes as a report warns that some hard-up households will be spending more than half their income on energy when bills soar.
While the average low-income family will be forking out 18% of their earnings on gas and electricity after April, this figure rises to 54% for single-adult households.
Katie Schmuecker, of the Joseph Rowntree Foundation which carried out the analysis, called on the Government to stop the rising cost of living from knocking people off their feet.
She added: “The alarm is sounding and the case for targeted support to help people on the lowest incomes couldn’t be clearer.”
The foundation has also found about 1.8 million children are growing up in very deep poverty, a rise of 500,000 between 2011/12 and 2019/20.
Ms Schmuecker added: “No childhood should be defined by a daily struggle to afford the basics.
“The fact that more children are in poverty and sinking deeper into poverty should shame us all.”