Complaints about energy companies have soared to their highest ever level, according to the Ombudsman Services.

During the first half of this year, complaints about all energy companies more than doubled from the previous six-month total of 10,598 to an all-time high of 22,671. (See's How to Complain guide for what to do if you have a gripe with a firm.)

Complaints also reached a record for a single month, with 4,124 unhappy customers registering their frustrations in June, an increase of 216% on the same time last year.(Join our free Cheap Energy Club to get the best deal on your gas and electricity.)

Billing-related issues topped the list, accounting for 84% (19,009) of all complaints made between January and June 2014, up 113% from the numbers recorded between July and December last year.

The second largest issue centred on transferring tariff with 13% (2,998) people complaining. Again, this figure's up 146% on those lodged in the second half of 2013.

People 'more empowered' to complain

Chief energy ombudsman Lewis Shand Smith says: "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 Department of Energy and Climate Change spokesman says: "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."

The energy market has come under fire recently and the big six face increasing pressure to improve their practices.

Just last month, energy watchdog Ofgem warned Npower to resolve its billing problems by the end of August or halt all telephone sales to new customers (see the MSE news story: Npower faces Ofgem investigation).

The regulator also confirmed last month that it was referring the energy market for a full competition investigation to help the market become simpler, clearer and fairer for all.