The BBC reports:
Ofgem is to investigate recent energy price rises, as it says they have significantly widened suppliers' profit margins.
The watchdog said that the net profit margin of £65 per typical customer in September was now £90, a 38% rise.
The calculations take into account price rises announced by three of the "big six" suppliers in recent weeks.
The regulator said it was asking if "companies are playing it straight with consumers" after the latest figures showed a 38% rise in profit margins from the typical dual-fuel customer in the last three months