Britain's bitterly cold winter boosted the profits of British Gas owner Centrica after the company raised tariffs by 6% in December.
The rise in profits, from £345 million in the same period last year, is likely to spark anger despite the company pledging to halt further tariff hikes.
Campaigners have called for the company to go further and cut prices.
Centrica chief executive Sam Laidlaw said: "With our customers using more gas to stay warm during the unusually cold winter, we're doing everything we can to help them keep their energy costs under control and make bills simpler and clearer."
More top news
A major search operation has been launched for 25-year-old junior doctor Rose Polge who has not been seen since Friday.
Former Liberal Democrat MP Lord Avebury, known for campaigning for democratic and human rights, has died aged 87.
A late Danny Welbeck header gave Arsenal a vital win over ten man Leicester at the Emirates.