Wholesale energy prices have been blamed for the increases, but the supplier has stated that it is not planning to introduce any further rises for standard tariff customers this year.
Phil Bentley, managing director of British Gas, said that the company "very much regrets" the move.
He explained: "The simple fact though, is that we have entered an era of unprecedented high world energy prices.
"The only answer to cope with higher energy prices, I'm afraid, is for all of us to be more energy efficient and we will be contacting all our British Gas customers to show how they can save energy to try and offset these price rises."
EDF Energy increased its gas and electricity costs by 22 per cent and 17 per cent respectively.
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