Complaints against energy companies have surged due to rising prices and poor customer service, according to a consumer panel. Data put together by Consumer Futures showed npower was the most complained about "big six" company.
"The vast majority" of customers are "happy" with their energy providers service, despite a surge in the number of complaints against the "Big Six" companies, an industry trade group said.
A spokesman for Energy UK defended companies like npower and E.ON and claimed they "take their relationship with customers extremely seriously".
The vast majority of energy customers are happy with the service they get with only around one in every 1,400 customers likely to need to contact their supplier about a problem.
Most complaints only need a phone call to sort out - around four out of five queries are resolved by the end of the next working day - but, if the problem cannot be resolved, the energy ombudsman is there to ensure problems get fixed.
Energy companies take their relationship with customers extremely seriously and work hard to improve customer service.
Energy companies will need to "put customers first" and be "much more transparent" about their profits if they want to win back public confidence, the head of Citizens Advice said.
Gillian Guy said they were dealing with 90,000 problems to do with energy companies each year as customers were hit with "unclear" bills.
Price hikes of 36% over the last three years, coupled with poor customer service, has compounded the lack of trust in energy firms as households struggle to afford to have a warm home.
The Citizens Advice service deals with 90,000 energy problems each year. People are being hit with large back bills, find their bill unclear and direct debit customers are frustrated companies are holding onto their money when they're in credit.
Energy companies need to put customers first and be much more transparent about where they make their profits.