Customers who recently made a complaint to their energy supplier are less satisfied with how it was handled compared to two years ago, Ofgem has revealed, with Npower considered to be the worst supplier at handling complaints.

Ofgem runs a survey every two years to compare how suppliers deal with complaints. Since the last survey in 2014 the total number of complaints has fallen by around half, but how satisfied people are with the way the complaint was handled has dropped significantly.

Of the 'big six' energy suppliers, Npower had the highest proportion of 'very dissatisfied' customers, with 67% of people who'd complained giving that response. Scottish Power were close behind with 64%.

This comes after Ofgem ordered Npower to pay £26 million for billing and complaint handling failures in December last year, and in April this year Scottish Power paid out £18 million for similar failures.

Of the smaller suppliers, First Utility has the highest proportion of "very dissatisfied" customers, with 63% of people who'd complained giving that response. Utility Warehouse wasn't far behind with 53% of customers saying they were "very dissatisfied" with the way their compliant was handled.

SSE, E.on and EDF Energy fared better but still haven't seen much of an improvement since 2014.

Npower is yet to respond to's request for a comment. We will update this story when we hear back.

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Complaints handling performance among the 'big six' energy suppliers

  Npower Scottish Power SSE E.on EDF British Gas
Very satisfied 3% 4% 20% 16% 17% 11%
Quite satisfied 8% 9% 23% 19% 15% 18%
Neither/nor 6% 9% 16% 14% 15% 12%
Quite dissatisfied 16% 13% 14% 16% 16% 17%
Very dissatisfied 67% 64% 26% 34% 35% 41%
Don't know 0% 1% 1% 1% 2% 1%

In other areas suppliers had performed well since the last survey. More than three quarters of people (77%) said that it was easy to find the right contact details to make a complaint, up from 65% in 2014.

Nevertheless, after initial contact with their supplier, customers reported that the service deteriorated. Two thirds of people surveyed said they weren't given a named contact at their supplier to get in touch with about the complaint and that they didn't receive follow up information at an agreed time.

At the end of the complaint, 42% of people whose case had been closed by the supplier thought it remained unresolved.

Most tellingly, 52% of people surveyed had or were planning to switch as a result of their customer service experience. The majority of Npower and Scottish Power domestic customers surveyed who complained (71% and 59% respectively) said they had or were planning to switch as a result of their experience.

Ofgem has said it encourages people to switch but that energy suppliers should also provide a minimum standard of customer service.

Dermot Nolan, chief executive of Ofgem, has written to all suppliers surveyed to demand an improvement.

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