Around eight million British Gas customers face paying out more from next month.
The energy supplier is hiking up its tariffs by an average of 7 per cent.
Households bills for gas and electricity will increase from December 10.
It will lead to rise of £1.50 on the average weekly dual-fuel bill.
The increases apply to customers on standard and variable tariffs.
The company said rising wholesale prices had forced it to lift the bills, but vowed not to apply the increase to the company's 300,000 most vulnerable customers, such as the poorest pensioners.
The move follows a price lift by utility giant Scottish & Southern at the end of last month. The firm said it would put up its gas bills by 9 per cent from December 1.