CUSTOMER complaints about energy companies have increased to their highest ever level, according to the Energy Ombudsman.
In the first half of the year, cases more than doubled from the previous six-month total of 10,598 to an all-time high of 22,671.
The figures show complaints also reached a record for a single month, with 4,124 registered in June.
That was an increase of 216 per cent from June last year.
Billing-related issues continue to be the biggest source of pain for consumers, accounting for 19,009 of the complaints made between January and June 2014.
Transfer issues were the second largest cause, with 2,988 issues.
Energy watchdog Ofgem last month warned Npower to resolve its billing problems by the end of August or halt all telephone sales to new customers.
Lewis Shand Smith, chief energy ombudsman, said: "The spike in complaints is in part a result of the rising cost of living, but also as a result of consumers becoming more aware of their rights and feeling more empowered to act and fight for a fair deal.
"Addressing these concerns is crucial to restoring consumer confidence in the sector."
A spokesman for Energy UK added: "The energy industry works hard to provide the best service for its customers but in an industry serving 27 million households sometimes things go wrong.
"However, no one wants to see complaints rise and each complaint is taken very seriously with companies working hard and investing in resources and new systems to resolve issues as quickly as possible.
"Most complaints are dealt with by the end of the next working day with no more than a phone call."