The regulator said it has published the figures to “increase the pressure on them to improve”, and to make it easier for customers to compare the major suppliers’ records on dealing with complaints.
Npower and SSE top the complaints resolution table for the third quarter of 2014, resolving 97.19 per cent and 97.02 per cent of customer complaints, respectively, within eight weeks.
Scottish Power (92 per cent) and Eon (93.8 per cent) were the worst of the major suppliers, while British Gas and EDF Energy resolved 94.8 per cent and 96 per cent of complaints, respectively, within the eight week timeframe.
The eight week period was used by the regulator because any complaint not resolved within that time can then be referred on to the Energy Ombudsman for investigation.
Last year, a total of 5.5 million complaints were made against the six largest energy suppliers, while the first nine months of 2014 have seen almost 4.9 million complaints. Ofgem estimates the full year total will exceed that of 2013.
The publication of the complaints data comes on the back of a customer survey in September which showed that more than half of consumers were not satisfied with their complaints handling process of the big six suppliers.
Following the report, Ofgem demanded suppliers fixed their “frankly awful” customer service and publish independent audits of their process for closing complaints by the end of November.
The regulator added it would bring forward its next customer complaints survey, after which it will decide if further action is necessary.
Ofgem’s senior partner in charge of enforcement Sarah Harrison said: “Suppliers must turn around their awful record on dealing with customer complaints.
“More visibility on complaint handling performance as well as our investigations into Npower and Scottish Power increases the pressure on suppliers to improve in this area.”
Last week the regulator threatened Scottish Power with a sales ban over its poor customer service and launched an investigation into the supplier.