Ofgem has written to energy suppliers demanding details of how they will put their price increases into action, following the news that some EDF customers were overcharged as a result of problems with their automated meter reading system.

The watchdog wants to check that the customers of other Big Six firms aren’t at risk from the same mistake, which has led EDF to compensate affected customers by a total of almost £200,000.

A spokesperson for Ofgem said: “We have written to suppliers asking each of them to provide details of the approach they take to apportioning prices increases and an explanation of the checks they employ to ensure accuracy. We also want to understand the way in which estimated and actual bills are reconciled.”

Five of the Big Six energy companies have jumped on the price increase bandwagon, with SSE, Scottish Power, E.ON and npower announcing them, while British Gas’ higher prices come into effect today.

Ofgem says it wants information so that it can be confident that customers are being billed properly where there has been a price rise.

The spokesperson added: “We want suppliers to explain what mechanisms they use when prices are raised to ensure that consumers only pay the higher price for units consumed following the price increase.”

E.ON, npower, British Gas and Scottish Power all confirmed they have received the letter and will be replying by September 12, when Ofgem has demanded a reply, while SSE told ELN: “We are cooperating with Ofgem to provide the information they’ve requested.”