EDF Energy on Friday became Britain's first big energy supplier to announce household winter gas price cuts, breaking ranks with three rivals who have opted to freeze prices instead.
British wholesale gas and electricity prices have risen about 30 and 40 percent respectively since June, along with a rebound in other commodities such as coal, leading to speculation that some energy suppliers could raise prices.
But EDF's move may ramp up pressure on the remaining "Big Six" firms, Iberdrola's Scottish Power and RWE's npower, to also cut prices, if not freeze them.
British Gas owner Centrica, Britain's biggest energy supplier with 6 million customers, SSE and E.ON have all pledged to freeze prices this winter.
EDF Energy said it will cut UK variable gas prices by 5.2 percent from Jan. 6 before the coldest winter weather bites in gas-heating reliant Britain.
From January, the firm's prepayment customers will get a 12.9 percent gas price cut.
But EDF is holding variable electricity prices until March 1, before raising by 8.4 percent - which none of the other suppliers have yet announced.
"Electricity costs have been rising for some time, but gas prices are not facing the same pressures," the company said in a statement.
France's EDF, the parent company of EDF Energy, has lost nearly 30 percent of its stock market value this year and has warned of lower 2017 earnings due to an expected drop in power prices, while safety probes force it to idle chunks of its domestic nuclear output. [nL5N1EA1YN]
Taken together, the changes mean EDF Energy's new standard dual fuel direct debit price will rise by 1.2 percent to 1,082 pounds a year, below forecast inflation.
Energy bills have doubled in Britain over the past decade to about 1,200 pounds ($1,640) a year, and the government has said it could intervene in the market if it believes prices are too high.
(Reporting by Oleg Vukmanovic and Nina Chestney; Editing by Alexander Smith/Ruth Pitchford)