Scottish Power’s boss has urged the government to give households £1,000 to deal with soaring energy bills.
Keith Anderson, the utility’s chief executive, said the current proposals for a £200 loan and £150 in council tax relief to help would not be “anywhere near enough" if the rate cap goes up again in October.
UK energy bills are currently capped at £1,971 but are subject to adjustments every six months to help suppliers deal with changing wholesale costs.
In October, Anderson expects the cap to rise to between £2,500 and £3,000, which he predicts will lead to a wave of people unable to pay bills.
Anderson had called for a social tariff in April when the heads of the UK’s energy supplies told MPs of horrific consequences for many households if prices rise again.
"We need to be realistic about the gravity of the situation - around 40% of UK households, potentially 10 million homes, could be in fuel poverty this winter," Anderson said in an interview today with the BBC.
He said the £1,000 grant for the most vulnerable would cost £10bn and be funded by a levy of £40 annually on household energy bills for the next decade.
Households on pre-payment meters and those in receipt of benefits would be eligible for the discount, he added.
Gas demand is very seasonal and since March prices have fallen sharply to around 150p/therm from 500p/therm, but Anderson warned that more companies will leave the market or go bust if the regulator does not reflect the prices that suppliers paid in the preceding winter in the new price cap.
Ofgem told the BBC that it is "too soon" to predict the level of the price cap from October.
A government spokesman said: "We recognise the pressures people are facing with the cost of living, which is why we have set out a £22bn package of support, including rebates and energy bill reductions.
"We also urge energy companies to support their customers as we manage the impact of high global gas prices.
"We are also supporting vulnerable households through initiatives such as the £500m Household Support Fund and the Warm Home Discount, with the energy price cap continuing to insulate millions of families from high global gas prices."