More complaints were made about Npower than any other large energy supplier last year. In fact the firm had 10 times as many complaints as rival SSE in the last three months of the year, according to figures compiled by Citizens Advice.
The charity reports today that Npower remained firmly at the bottom of the energy complaints league table every quarter in 2013 and has been since the end of 2012.
Bills arriving late, payments being stopped and new accounts not being set up are just some of the problems Npower customers are experiencing with its new billing system.
Citizens Advice chief executive Gillian Guy said: “Things are getting worse not better for Npower customers. For over a year now some npower customers have been finding their finances thrown into chaos.
“It is unacceptable that it 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.
“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.”
Meanwhile, according to the Ombudsman Services, 3,892 people complained about their energy supplier last month, three times higher than in April 2013.
John Robertson MP, who sits on the Energy select committee, said: “People are sick and tired of being ripped off and receiving nothing in return. They get terrible customer service and are constantly having to chase their supplier after mistakes have been made.
“Arrogant energy barons seem to have forgotten that people are paying for a service and expect a good one, having forked out over £1,000 for it.”
Last year, it was found that energy companies’ annual profits had risen by 73 per cent in three years to £3.7 billion.