Energy supplier E.ON is to reduce its standard gas price by an average of 3.5 per cent with immediate effect.
The company, which has 4.5 million household customers, said the move is equivalent to £24 off the average annual gas bill, or two weeks' gas use.
E.ON also launched what it said was the country's cheapest energy tariff, a new one-year fixed dual-fuel product with an average annual price of £923.
The move increases the pressure on the other Big Six energy suppliers - British Gas, SSE, Scottish Power, EDF and npower.
E.ON UK chief executive Tony Cocker said: "Given the possibility of a price freeze, we are undoubtedly taking a risk today but we always put our customers first."
The final of the 'Big 6' energy firms to cut prices - EDF - has announced it is reducing gas tariffs by just 1.3%.
Despite an investigation from the Competition and Markets Authority the Energy Secretary appears to have come to his own conclusions.