In total, only 52 per cent of consumers said that they were happy with the services they received on meter reading - and just 61 per cent expressed satisfaction with the billing process.
Of all the companies surveyed, Powergen improved most in terms of customer service ratings. The provider was voted worst supplier for customer service a year ago - but it has managed to turn its image around by investing heavily in customer care and by moving its call centres back to the UK.
"The key thing for the energy giants now is to take stock and listen to what customers are saying," Ann Robinson, an official at the company that carried out the research, said.
"But more importantly, customers also need to carry on taking matters into their own hands. Strangely enough, the one aspect of service that the suppliers are getting right is the transfer of customer accounts. This is the language that the industry understands and responds to best."
Only 38 per cent of Brits say that they would recommend their energy supplier to a friend.
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