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.
More top news
The late Bernard Jordan, who 'escaped' from his care home to travel to the D-Day commemorations, has left his entire estate to the RNLI.
UK to be "very cold indeed" over the coming days due to bitter northeasterly winds.
Luis Figo will run a campaign for change after announcing his intention to challenge Sepp Blatter for the Fifa presidency