British Gas has announced it is to hike its electricity tariffs by 12.5% in September in a move affecting 3.1million customers.
The Big Six energy giant confirmed the price rise, which will take effect on September 15, after a blunder on Monday saw the group mistakenly publish an incomplete statement about increasing electricity tariffs on its website.
Centrica-owned British Gas said the price rise is its first since November 2013 and the group pledged to help protect more than 200,000 vulnerable customers from the increase.
Details of the increase comes as British Gas owner Centrica posted half-year results revealing that earnings from its consumer business plunged by more than a quarter after it lost 377,000 UK customer accounts in the first half.
Underlying operating profits from its UK home energy supply arm tumbled 26% to £381 million as the group said it was also hit by warmer than normal temperatures and the pre-payment tariff cap.
Centrica's overall underlying operating profits were 4% lower at £816 million for the six months to June 30.
The group said it held off from the price rise a for "up to six months longer than some of our competitors".
The price hike will mean an average dual fuel bill for a typical annual household tariff will rise by £76 to £1,120 - a 7.3% increase, according to British Gas.