There has been "some evidence" of a profit rise for the Big Six caused by higher bills for consumers, the energy regulator said.
However, bill increases in 2012 were caused by a rise in wholesale prices, a report from Ofgem found.
According to the report:
- There was "some evidence of rising profit margins" - attributed to higher gas and electricity prices, rather than lower costs.
- Prices on the wholesale market rose by 14%, causing the rise in household bills.
- Increases in the cost of transmission, distribution and payments to Government, up a combined 20%, were added onto bills.
- A rise in profits in 2011/12 was partly caused by higher gas consumption during two winters which were colder than average, compared to 2011, which was warmer.