The latest report by the Competition and Markets Authority (CMA) showing more than 70% of energy consumers had never switched tariffs, was of grave concern, according to the Energy Advice Line.
A survey of 7,000 domestic energy customers carried out by the CMA as part of its probe into the energy market, also found that more than one-third of respondents had never considered switching supplier.
This was despite the fact that customers of the Big Six energy companies could have saved hundreds of pounds by switching to a rival firm.
"These findings are extremely alarming," said Julian Morgan, managing director of the Energy Advice Line.
"Yet another investigation has proved that switching suppliers has significant financial benefits, yet millions of customers are still failing to do it.
"Urgent action is now needed to persuade customers - in the strongest possible terms - to shop around for their energy, just as they do for all their other significant household purchases.
"Failing to do this is costing them considerable sums of money that most people simply can't afford to lose."
The CMA report, the culmination of a two-year, £80 million investigation of the energy industry, found that:
- 36% of those surveyed did not know it was possible to change tariff, payment method, and supplier
- 34% said they had never considered switching supplier
- 56% said they had never switching supplier
- 72% said they had never switching tariff
Mr Morgan welcomed the report's finding that third party internediaries, such as the Energy Advice Line, "significantly reduce search and switching costs for domestic customers by providing an easy means to gain personalised quotes, on a comparable basis, from a range of different suppliers."
But he rejected one of the report's recommendations for a national database of customers who had not switched over the past three years. This would see rival firms send their deals to the listed customers in the post.
"This would be a nightmare for consumers, who would be inundated with confusing offers from rival suppliers desperately competing for business," Mr Morgan said. "This would not help consumer engagement with the energy market, and could well have the opposite effect - all their communications could end up being ignored.
"As the CMA says itself, independent and reliable services like the Energy Advice Line are the quicklest, easiest and cheapest way to shop around for the best deals and change suppliers."
The Energy Advice Line is one of the UK's leading price comparison and switching services for business and domestic energy customers. It is also an advocate for energy market reform and has campaigned for a better deal for energy users, including callling for a ban on cold calling and changes to regulations to make it easier for all consumers to switch suppliers.
The service is completely independent and free. Consumers can quickly and simply search the market for the best available energy deals from an extensive panel of small and large energy suppliers. The service also offers a free advice line for business energy customers.
For further information visit energyadviceline.org.uk