E.ON blames costs as it follows others in putting up prices

The firm said the increase will add 16p a day to its dual fuel customers, adding that wholesale energy prices have soared by 35 per cent since last Spring.

Managing director Graham Bartlett said: "It's been over two years since we last increased our prices, and, unlike other companies, we held off from increasing them during the incredibly cold temperatures we saw in late November and December.

"But we now have no option but to make this change due to increases in the prices we pay for gas and electricity, although our customers won't actually see the increases until next month."

E.ON said more than one in five of its 5.3 million customers would not be affected by yesterday's announcement, which follows a string of price rises by leading energy companies in recent weeks.

The latest firm to announce price increases was npower, which said last month that household gas and electricity bills will rise by an average of 5 per cent.

Richard Hall, energy expert at Consumer Focus, said: "E.ON's customers will, sadly, not be shocked that it has followed in the footsteps of other suppliers' price increases.

"However, the fact that these rises aren't unexpected won't make it any easier for cash-strapped consumers to afford their higher bills.

"Consumers simply don't trust that suppliers are asking them to pay a fair price for their energy.

"With high prices, a complex market, and consumers being asked to pay billions of pounds to improve our energy supply, it is essential that confidence in energy prices is improved.

"Ofgem's review of the market needs to meet these high expectations."