Complaints to energy giant EDF, rose by 80% with 89,916 complaints received in the year to September 2012.
This equates to nearly 15.8 complaints for every 1000 EDF customers - up from 8.86 in 2011.
The news comes on top of the firm's massive, above inflation, 11% price hike announced last week adding around £120 to the average energy bill.
Most energy firms blame the rises on four factors:
1) The worldwide rise in wholesale gas prices.
British Gas estimates that wholesale gas price will be 13% higher this winter compared to last winter.
2) Delivering the energy.
The price charged by National Grid for using its power lines and pipes has increased by 9%.
3) Environmental regulations now add around 10% to the average bill.
This is the cost of insulation grants, solar power and other so-called "green" subsidies.
4) Energy firms reinvestment in upgrading infrastructure - new power stations, wind farms etc.
Energy firms work on a typical operating net profit margin of around 3.4%.
They claim the price hikes will not make much difference to this!