British Gas has revealed record half-year profits of £970m after Ofgem allowed the gas and electricity supplier to make more money from household bills.

Operating profits for the first six months of 2023 were 10 times the £98m made in the same period last year, surging past a previous record of £585m.

The increase was driven by a £500m boost from changes by the energy regulator to the price cap.

This raised how much suppliers could claim from household bills to make up for costs incurred during the pandemic, allowing British Gas to recover more of the costs it incurred for taking on customers from failed rivals.

Chris O’Shea, Centrica’s chief executive, insisted the large profit at British Gas was a “one-off” and largely the result of technical changes made by Ofgem to the energy price cap, which limits how much suppliers can charge consumers.

However, trade unions and Labour politicians claimed the company is “laughing all the way to the bank” at a time when millions of families are struggling to pay their bills.

Referring to Centrica’s profits, Ed Miliband, Labour’s shadow energy secretary, called for higher windfall taxes.

He said: “The Conservatives’ windfall tax has as many holes as a Swiss cheese.”

The company increased its dividend by a third to 1.33p per share and announced a £450m extension to a previous share buyback, taking the total amount to £1bn.