Warnings over a "long, cold winter" for the elderly and hard-up have grown after Britain's biggest energy supplier hiked electricity and gas tariffs by an average of 6%.
With food bills rising and many people also facing higher mortgage costs, British Gas added to the pressure on households by putting an extra £80 on to its typical annual dual fuel bill.
A total of 8.5 million households will be affected from November 16, a move which British Gas said was due to rising costs largely outside its control.
However, the pre-winter increase comes months after parent company Centrica posted a 23% rise in half-year profits at its residential arm to £345 million.
Unions and consumer groups attacked British Gas and called on the Government to take urgent action to tackle rising fuel prices.
Unite general secretary Len McCluskey said: "With winter approaching, low-waged people will now be terrified about how they are going to find another £80. Money from the poor is going to the pockets of Centrica shareholders. This is further shameful abuse by out of control, greedy fuel companies, sitting on piles of profit."
Consumer Focus recently said six million households in England were planning to cut back on their heating this winter because of cost worries. It has encouraged customers "to do what they can" to cut their bills by switching tariff, payment method and supplier.
Its director of energy Audrey Gallacher said no-one has managed to convince consumers of the necessity for price rises in the context of wholesale prices and company profits. She added: "We need much more focus on the big steps that Government and the regulator can take to insulate consumers from the effects of growing energy costs."
Consumer Focus said the price rise will see the company's average annual energy bills reach almost £1,265 for direct debit customers and more than £1,346 for cash and cheque customers.
SSE, which trades as Southern Electric, Swalec and Scottish Hydro, has already said it will increase tariffs by 9% on average on Monday, hitting about five million electricity customers and 3.4 million gas customers.