PRICE comparison websites, including Gocompare.com, founded by Cwmbran woman Hayley Parsons have bit back over claims they filter out tariffs from their energy searches from firms which do not pay commission.

The Big Deal website, which was set up last year to help consumers find cheaper energy bills, said all five of the major price comparison websites hid the cheapest deals from customers.

It said the sites ask users if they want to see tariffs they can switch to "today" or "now". Clicking "yes" filters out the deals which do not earn the comparison site a commission from the energy company.

The comparison sites have denied hiding the best deals and said their websites are transparent and in compliance with Ofgem's code of practice.

The Big Deal has written a letter of compaint to Compare the Market, Go Compare, uswitch, MoneySuperMarket and Confused.com after its research claimed that almost a third of deals were hidden.

The website has also sent its letter to Energy Secretary Ed Davey and said it wants the Competition and Markets Authority to expand its investigation of the the energy market to include the activities of price comparison websites.

The Big Deal said: "The price comparison sites are worth hundreds of millions of pounds, make huge profits and, with over five million people switching a year, are a major part of the energy market. Yet there is no transparency to how they make their money or how much they charge."

It quoted a poll by Populus which found that 43% of people did not realise that the sites charge energy companies a commission.

However, Jeremy Cryer, energy spokesperson at Gocompare.com, said: “The Big Deal’s findings just don’t stack up. We help consumers compare over 150 tariffs and make it clear on our results screen that, whilst many are available to buy through Gocompare.com, there are more tariffs available across the market and customers can view those tariffs without having to leave the results screen.

“By comparison, The Big Deal only provides people with access to one tariff with no guarantee at all that it is market leading. It doesn’t compare that tariff against any other deals, let alone the whole market, so anyone joining a collective switch scheme would still need to shop around to make sure that they are getting the best tariff for them and comparison sites are the single best way to do that quickly and easily.”

A spokesperson from comparethemarket.com, said: “Price comparison websites have been a driving force of greater competition and lower prices in the energy market. In under five minutes consumers can compare more than 100 tariffs, a process that would take weeks to research individually.

"Suppliers sometimes stipulate which tariffs they wish to sell on price comparison websites. Also, tariffs that are not in the main search engine could belong to new suppliers who are just soft launching their services and don’t want too much volume yet. Once all parties are confident that the provider in question is fully prepared to take on new customers the tariffs go into the main search engine. This is important due diligence to protect consumers, ensuring that providers have been appropriately tested and that products are fit for purpose."

However, The Big Deal wants price comparison firms to remove the "today" button option and publish the amount of commission received from each energy company.

Uswitch said: "We are fully accredited under the Ofgem Confidence Code, meaning that our results tables are always ordered by the savings a customer can make in a fair, independent and unbiased way. We are fully supportive of Ofgem's decision to strengthen the code to ensure that all price comparison websites operate to the same high standard.

"Customers have the clear option to compare plans across the whole energy market on our site. We do not pre-select a default answer when giving them this choice, nor do we in any way influence what they should select.

Dan Plant, editor-in-chief of MoneySuperMarket, said: "The option for customers to filter results to only see products they can buy through MoneySuperMarket.com is displayed clearly and prominently, and is necessary as some providers choose not to list products on comparison websites.

"This adheres to Ofgem's Confidence Code which sets out how energy should be compared. Currently the cheapest 10 tariffs on the market are shown to all customers using our website - switching to one of these would save many households hundreds of pounds per year."

Ofgem is planning tougher new rules in its code of conduct in order to make commission arrangements clearer.

A spokeswoman said: "Price comparison websites are a good place to start when you're shopping around for energy deals.

"Consumers value these services, and we believe they can help make the energy market more competitive.

"We are currently revising the Ofgem confidence code to push price comparison sites to higher standards of reliable information by making the whole of market comparison easier to see. And we're proposing tougher new rules to the code to make commission arrangements clearer."

Energy Secretary Ed Davey said some of the criticism of the websites was unfair but acknowledged that more needed to be done to encourage switching and improve competition.

"Some of the claims that are being made today are not actually fair to some of these websites. They are rather more transparent than they used to be before the confidence code was brought in," he told BBC Radio 4's World At One.

"The question always is 'Can we improve things?' I'm determined to improve things for consumers. We need to make sure that the tools people use to switch - like switching sites - are completely reliable."

Shadow energy secretary Caroline Flint said: "There is something clearly wrong when customers can't get full information to make the best choice possible for their energy.

"It is just another example of why we need to reform this market. People do not want to spend half of their waking day looking around for best deals because it is made so difficult."