EDF Energy was the most complained about of the ‘big six’ energy firms at the end of last year, according to figures demanded by regulator Ofgem.
The gas and electricity supplier received 8,072 complaints for each 100,000 customers in the final quarter of the year - more than double the 4,001 logged for the second most complained-about firm npower.
Britain's biggest energy supplier, British Gas, said it received 2,285 complaints per 100,000 accounts, while E.ON posted 3,023, SSE 1,435 and Scottish Power 1,359.
Under new Ofgem rules, the big energy firms must publish quarterly complaints data on their websites, including information about how many complaints were received and how quickly grievances were dealt with.
In its last quarterly report in July, watchdog Consumer Focus also found EDF was the most complained about of the energy giants after it was the only one of the six to see an increase in complaints last year.
Consumer Focus compiled ratings based on figures from the Citizens Advice Bureau, the ombudsman and its own information from case workers dealing with vulnerable people.