EDF had the most complaints of the big six energy companies at the end of last year, according to figures demanded by regulator Ofgem.
The energy giant received 8,072 complaints for every 100,000 customers in the final three months of 2012 – more than double the 4,001 logged by rival Npower, which had the second-highest number of complaints.
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.
- EDF received 8,072 complaints per 100,000 accounts
- Npower, 4,001
- E.on, 3,023
- British Gas, 2,285
- Scottish and Southern Energy (SSE), 1,435
- Scottish Power, 1,359
E.on, Scottish Power and SSE were the only companies to provide figures for the previous quarter. All three saw their complaints rise, although numbers traditionally increase during winter.
The data showed EDF and E.on were the quickest in dealing with complaints, with both managing to resolve 92.3% of complaints by the end of the next working day.
'Service not up to standard'
Ofgem consumer policy partner Philip Cullum says: "Ofgem is now shining a spotlight on individual supplier performance by getting suppliers to publish better data, more often and more prominently.
"This should mean that suppliers improve the way they handle complaints and that the things they learn from complainants lead to better services."
An EDF spokesman says: "We recognise that last year our customer service levels were not up to the high standard we expect and our customers deserve.
"However, we're pleased to report our service levels have improved significantly over the last six months and our new systems are delivering clear benefits to our customers through clearer, more accurate bills and the introduction of better online services."