COMPLAINTS to Worcester-based energy giant Npower have soared by 300 per cent in the past two years.

The power company received 306 complaints for every 100,000 customers from October to December last year – three times as many as its nearest rival, Scottish Power and ten times as many as Scottish and Southern Energy.

The firm – which has 5.9 million customers throughout the UK – has topped polls of complaint figures since the end of 2012, with common gripes including bills arriving late, direct debits being cancelled without warning and new accounts not being set up.

In January 2012 the company recorded only about 100 complaints per 100,000 customers, but this has tripled in less than two years.

This is the latest in a series of blows for Npower, which has come under fire in recent months for a 10.4 per cent price rise and a new computer system causing a rash of problems with bills.

Citizens Advice Bureau chief executive Gillian Guy branded the findings “unacceptable”.

"For well over a year now some Npower customers have been finding their finances thrown into chaos,” she said.

“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."

Npower’s director of domestic retail business Roger Hattam insisted the company was working to tackle the problem.

"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,” he said.

"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."

Scottish Power was the second most complained about power firm, receiving 100.5 complaints per 100,000 customers, followed by EDF at 62 and E.ON at 55.8.

British Gas was the second best-performing supplier, receiving only 53.7 complaints per 100,000 customers while Scottish and Southern Energy topped the poll at only 31.5.

The Citizens Advice Bureau urged customers to complain if they experience a problem with their energy provider and said people who have spent time sorting out bungled power bills should ask for compensation from their supplier.