In a meeting yesterday, Barker asked the major suppliers to work with the government to ensure customers are not being over-charged via direct debits.
At the request of the Department of Energy and Climate Change (Decc), Energy UK has agreed to develop direct debit best practice proposals.
The suppliers have also been asked to provide information on how they currently deal with credit balances, and how much of their customers’ money they hold at any one time.
Barker said: “The better energy companies will now automatically refund your cash if you build up more money than required to meet your normal bill or will pay you interest if you are in surplus.
“However, it looks like some companies aren’t doing that.”
The government said it expects to see the energy companies “treating their consumers fairly, including being more transparent about their processes for returning credit balances to consumers”.
Richard Lloyd, executive director at Which?, said: “With trust at an all time low, energy companies must quickly deliver on this commitment to promptly refund consumers who are in credit with their direct debit accounts.”
He added: “Some energy companies already automatically refund even very low credit balances, so there’s no reason why the entire industry can’t follow suit.
“All companies need to play fair and charge more accurately.”
Representatives from Eon, SSE, Scottish Power, Npower, EDF Energy, British Gas, Consumer Futures and Which? all attended the meeting.