British Gas, owned by Centrica, is putting up its domestic gas and electricity bills from 18 August.
Gas bills will rise by an average of 18% and electricity bills by an average of 16%, costing an extra £190 a year for the average dual fuel customer.
The company blamed the rising wholesale cost of gas, which has gone up by 30% since last winter.
In June, Scottish Power announced it would raise the cost of gas by 19% and the cost of electricity by 10%.
British Gas Managing Director, Phil Bentley, said its bills were being driven higher by the fact that the company buys 50% of its gas on the international wholesale market.
“We are buying in a global energy market and have to pay the market rate,” he said.
“Rising wholesale costs is an issue facing all energy suppliers,” he added.
Centrica had already warned that it was likely to raise prices this year. In May, the company said its customers were not paying enough to reflect the increased cost of gas on the wholesale markets.
The latest rise in energy bills, which is likely to be followed by other big energy suppliers, comes after a round of increases last winter which saw British Gas put its charges up by 7% in December.
