Energy bills will rise to reflect soaring wholesale energy prices, the energy regulator has warned.
A price cap limits the impact of rising energy costs for customers, but Ofgem said this would increase.
Chief executive Jonathan Brearley said the cap was “designed to reflect fair costs and therefore will need to adjust over time”.
Nine UK energy suppliers collapsed last month and Mr Brearley said more could follow.
“Given the continued volatility in the market, it is likely more suppliers will exit the market,” he told a conference organised by Energy UK.
Natural gas prices are at record highs as economies around the world begin to recover from the Covid crisis.
As a result, firms are running into trouble because they have agreed to sell gas at less than the price it now costs them to buy it.
More than 1.7 million customers saw their energy provider go bust in September.
They have already seen annual bill increases of hundreds of pounds when they moved to a new provider and away from whichever low-rate fixed deal their supplier had offered.
Ofgem’s advice to those affected is that they should wait for the regulator to appoint a new supplier and refrain from switching in the meantime.
It says customers can rely on their energy supply as normal.
The warning from Ofgem’s Mr Brearley came after analysts Cornwall Insight predicted that household energy bills could rise by hundreds of pounds next year.
They said the energy price cap, which works by limiting how much firms can charge domestic customers for a unit of gas, could soar by £400 in the spring to about £1,660.
That is about 30% higher than the record £1,277 level for the cap set for winter 2021-22, which began at the start of October.