The owner of British Gas has increased profits at its residential arm by 23 per cent in a move fanning flames of anger over recent price hikes.

Centrica said profits at British Gas Residential, which has 15.8 million energy accounts in the UK, lifted to £345 million in the six months to June 30 after volumes were boosted by the cool start to the summer.

But the UK's biggest energy supplier also benefited from higher prices because, while it dropped its standard electricity prices by 5 per cent in January, this did not cancel out a 16 per cent rise in August, when gas bills also went up by 18 per cent.

Consumer Focus has accused utility companies of being quick to pass on rising wholesale costs to consumers but being slow to drop prices when they fall and today's bumper profits haul is likely to provoke further outrage.

Profits at its residential arm are also higher because of weak figures a year ago when it delayed passing on price rises to customers, meaning it was supplying at a loss.