The French firm is one of Britain's biggest energy suppliers and its increases, which come into immediate effect, will mean typical customers on a dual fuel tariff will pay £3.97 a week more for their energy.

EDF blamed record wholesale energy costs for the price hikes, saying wholesale energy prices had increased by 70% for coal, 63% for gas and 47% for electricity since it last increased its prices in January.

Eva Eisenschimmel, chief operating officer of EDF Energy customers branch, said: "We have been absorbing some of these costs in recent months, but we now have to pass on some of the resulting rise in wholesale costs to our customers.

"While the rise in wholesale prices is out of our control, we have been doing everything possible to keep our own costs in check.

"In this difficult economic climate we are very concerned by the impact any price rise will have, especially for those on low incomes. As a result, we have expanded the number of customers on our Energy Assist social tariff by a half, bringing the total to 100,000 customers.

"We are also working with the Government on new initiatives to help low-income households this winter. We have also launched a new fixed-price tariff for our customers who want security in their budgeting.

"In addition, we were the first supplier to align electricity prepayment customer tariffs to that of credit meter customer tariffs.

"Further, we will also continue to help customers keep control of their costs through energy efficiency advice and our range of products including Read, Reduce, Reward."