Customer complaints about energy companies have soared to their highest ever level, according to the Energy Ombudsman.
During the first half of the year complaints more than doubled from the previous six-month total of 10,598 to an all-time high of 22,671.
The figures show that complaints made to the ombudsman about energy companies also reached a record for a single month, with 4,124 unhappy consumers registering their frustrations in June.
This is an increase of 216% from June last year.
Billing-related issues continue to be the biggest source of pain for consumers, accounting for 84% (19,009) of the complaints made between January and June 2014.
Transfer issues were t he second largest cause for complaints at 13% (2,988).
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.
Chief Energy Ombudsman Lewis Shand Smith 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."
The ombudsman service was founded in 2002.
A Department of Energy and Climate Change spokesman said: " It is unacceptable that so many people have needed to complain about their energy suppliers.
"Energy companies need to realise that people will not tolerate poor service and are switching suppliers in unprecedented numbers, particularly to small suppliers whose numbers have nearly trebled since 2010."
A spokesman for Energy UK said: "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.
"The industry will be consulting stakeholders this summer about the complaints it cannot fix in 48 hours.
"If any customer is concerned or has a problem with their energy supplier they should speak to the companies first. A simple guide to helping people resolve their problems can be found at www.energymadeclear.com/energy-and-you/what-to-do-when-things-go-wrong."