Energy giant EDF is to increase its dual fuel tariff by 7.2% from June, gas prices by 5.5% and electricity by 9%, affecting 1.5 million customers.
The company, which has 3.3 million customers, said the industry was facing "significant" cost reductions.
EDF announced a 1.2% increase in dual fuel tariffs in December, saying the combined effect of both changes is 8.5%.
The company also launched a new three-year fixed deal, including a year's free boiler insurance.
Chief executive Vincent de Rivaz said: "I know that price rises are never welcome, but the industry is facing significant cost increases. To be a sustainable and responsible business, we aim to make a fair margin in supplying customers.
"This fair margin allows us to invest for the long term, in particular in good service, innovation and smart metering. It also allows us to help more customers choose the right tariff for them. We have cut all the costs under our control without compromising our customer service.
Last month SSE said it would be adding £73 to customers' bills with a 6.9% hike in its dual fuel price, a week after E.On revealed it was increasing its standard dual fuel prices by an average of 8.8%.