The profit margin for gas and electricity suppliers amounts to £100 per customer per year, it has been claimed.
The figures take into account energy suppliers buying their supplies 18 months in advance, with costs peaking last December.
Ofgem announced last year that it would be carrying out a regular analysis of the link between retail and wholesale energy prices.
The regulator's report also reiterates that there was no collusion between the big six energy firms on pricing policy.
It also claimed that there was no evidence that electric and gas firms passed on wholesale energy price increases to their customers but failed to reduce costs when prices began falling.
Yesterday, Scottish Power cut its gas and electricity prices by 7.5 per cent and three per cent respectively.
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