EDF Energy to put up gas prices by 15%
EDF Energy is to raise gas prices by 15.4% and electricity prices by 4.5% from 10 November, the company has announced.
It is the last of the "big six" energy companies to announce increases in prices for domestic customers.
It said it had absorbed wholesale price rises for as long as possible before being forced to raise costs for customers.
Regulator Ofgem is studying whether higher prices are justified.
"We have absorbed rising wholesale energy, network and other costs as long as possible but must reluctantly now pass some of these through to consumers," said Vincent de Rivaz, chief executive of EDF Energy.
The annual cost of a standard dual-fuel bill paid for by direct debit would rise to £1,165 from £1,051, the company said.
EDF follows the other five major energy suppliers - British Gas, Scottish Power, Scottish & Southern Energy, Npower and E.On - in announcing price rises.
The tariffs across the industry have included price rises of up to 18%.
"The fact that EDF Energy has made smaller and later hikes than other suppliers is welcome, but it will not soften the blow on those who are struggling on tight household budgets," said Mike O'Connor, chief executive of watchdog Consumer Focus.
The moves have prompted the energy regulator Ofgem to step up its investigation into pricing by the big six suppliers.
It has brought in the forensic accountants BDO to see if energy firms understated their retail profits to justify higher prices.
Mr de Rivaz said that "suspicion" of the industry needed to be addressed.
"We recognise there remains a widespread lack of understanding and suspicion of the industry as a whole, among the public, customers in general, politicians, regulators and others," he said.
"It is important this perception is addressed. The energy challenges Britain faces are far too important and can only be addressed in a world with trust, open dialogue and mutual understanding.
"If a Competition Commission inquiry is necessary to build this trust, then it is a step that should be taken."
Last month, EDF admitted that 100,000 customers had been overcharged owing to a seven-year fault on the company's automated telephone meter reading system.
The problems occurred at times when EDF changed its prices between October 2003 and May 2010. This led to £200,000 of overcharging, although customers affected are being reimbursed, including interest.
Mr de Rivas apologised for "service issues" suffered by some customers.
An analysis of entries on Twitter about customer service found that 11% were positive and 70% negative in relation to EDF, according to social media monitoring company Brandwatch.
The highest proportion of negative comments among the big six suppliers was 73% about Npower.
"Twitter is an exciting new venture for Npower and we are finding it an engaging way to talk to our customers," said a spokesman for the company.
Meanwhile, earlier this month, EDF said it had joined Scottish and Southern Energy and British Gas in halting unsolicited doorstep sales of gas and electricity contracts.
Heating costs contributed to the rising cost of living reported by the Office for National Statistics (ONS) on Wednesday.
The rate of inflation measured by the Consumer Prices Index (CPI) rose to 4.5%, from 4.4% in July. The Retail Prices Index (RPI) measure increased to 5.2% from 5%.
Debt advice service the Consumer Credit Counselling Service said that one in three people contacting the charity for help were in fuel poverty.
This is when a household is spending more than 10% of its income on heating.