EonEnergy giant E.ON made an extra £381 million in revenues after hitting gas customers with a 9.4% price rise shortly before the freezing weather set in.

Financial results from the first half of 2013 showed the German company cashed in as British families turned up the thermostats to keep out the cold amid the worst spring temperatures in decades.

Revenues were up 9% to £4.47 billion compared to the same period last year.

The Dusseldorf-based company said that Britain's gas consumption over the period increased by 10% due to the freeze, more than offsetting declines caused by new energy efficiency obligations and economic pressures facing customers.

It said the rise in sales was "primarily because of higher retail sales resulting from increased demand due to low temperatures, particularly in March".

Underlying earnings from the UK market rose 7% to £263 million.

E.ON, which has five million customers in Britain, wrote to households last December to warn that it was raising dual fuel prices by 8.7% and gas tariffs by 9.4%, as well as electricity by 7.7%.

However the energy giant saw overall profits plunge amid weak demand for power in Europe and increased competition from subsidised renewable energy.

Underlying net income slumped by a hefty 42% to 1.91 billion euro (£1.64 billion) but chief executive Johannes Teyssen said the performance was expected.

"A sober view of the situation indicates that, at least for 2013 and 2014, no recovery is in sight," Dr Teyssen added.

He said that the company was already responding as it cut costs, raised efficiency and mothballed some assets such as a recently closed gas-fired plant in Slovakia.

Dr Teyssen said E.ON was facing a difficult business and regulatory environment but that it still expected full-year underlying net income between 2.2 billion euro (£1.9 billion) and 2.6 billion euro (£2.2 billion).