The organisation also said that it could not act until it had proof of such activity.
Ofgem's spokesman said: "Britain has one of the most competitive energy markets in Europe, with changing market share between the companies, price differences and good levels of switching.
"We keep markets under constant review but we can only take action if we find evidence of anti-competitive behaviour."
It was recently revealed that chancellor of the exchequer Alistair Darling is planning to meet with the regulator to discuss rising energy prices in the UK.
The Times obtained a letter written by the chancellor to the body, stating that he wanted to better understand the link between wholesale energy markets and household energy bills.
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