Britain's biggest energy suppliers have denied claims of price-fixing.
Earlier this year, industry regulator Ofgem said that energy companies had not passed on falls in wholesale prices to consumers.
MPs asked the Big Six firms whether they accept the watchdog's statement that energy prices tend to rise more quickly with wholesale rises than they decline as a result of falls in wholesale costs, Environmental Data Interactive reported.
Responding, E.ON's regulation director Sara Vaughn said: "I think if you look at what Ofgem says they say there is 'some' evidence that prices move in that way ... it's not, if you like, a definitive conclusion."
Her comments were echoed by David Mannering of RWE npower, who added: "It's not clear cut at all, because [Ofgem has] made a number of assumptions." He argued that suppliers incur costs in changing their prices, and energy suppliers have to buy their energy in advance in bulk, meaning that they can’t respond instantly to a fall in wholesale prices.
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