ENERGY firm Npower is the UK's most complained-about major power supplier, new figures have said.
The company, which imposed the highest price hike last winter, received ten times as many complaints as its best performing rival.
Information from the Citizens Advice Bureau showed that between October and December last year, Npower was inundated with 306 complaints for every 100,000 customers.
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The figure is three times as many as the second worst performing supplier, Scottish Power, which attracted 100.5 complaints per 100,000 customers.
The revelation is the latest in a series of blows for the firm, which was heavily criticised when it imposed price rises of 10.4 per cent last October.
Its new billing system has also been blamed for causing widespread frustration and anger among customers, who have complained of being hit with inaccurate charges.
Roger Hattam, director of domestic retail business for Npower insisted the firm is tackling its customer service problems.
He said: "We wrote to all our customers during this period last year apologising for the impact on them of issues we have had with the implementation of our new billing system.
"We are making good progress in dealing with the root causes of this, but remain totally committed to resolving any problems this has created for our customers."
However, Gillian Guy, Citizens Advice chief executive, said people were bearing the brunt of poor service.
She said: "Things are getting worse for Npower customers.
"It is unacceptable that Npower has not yet sorted out the serious failings in its billing systems and customer service which are causing so many complaints and serious problems for its customers.
"For well over a year now some customers have been finding their finances thrown into chaos.
"Some are not receiving bills and others are ending up in debt because their direct debit was cancelled.
"Citizens Advice has asked Npower to make sure people affected get any appropriate compensation.
"Time and time again energy suppliers are letting customers down.
"People will not feel able to trust energy suppliers again if firms cannot get their house in order and deliver decent customer service."
Energy firm EDF was the third lowest scoring of the big six suppliers, receiving 62 complaints for every 100,000 customers, while Eon came fourth with 55.8.
Scottish and Southern Energy was the best performing of the firms attracting 31.5 complaints per 100,000 customers, while British Gas came second receiving 53.7 complaints.