Martin Lewis has given some urgent advice to more than 400,000 households after two energy firms collapsed this week.
Thousands of customers have been left without a supplier after Green Network Energy and Simplicity Energy ceased trading
Green Network Energy provided around 360,000 domestic customers with gas and electricity, while Simplicity Energy had around 50,000 customers - reports Mirror Online.
Ofgem, the energy regulator, said it would protect the customers of both failed businesses, including their credit balances.
Speaking on the ITV Money Show on Thursday, Martin Lewis said customers should not rush to act.
He said: "You don't need to do anything yet.
"Your supplier will remain the same for now, and, in a few weeks, Ofgem, the energy regulator, will automatically move you to a new company with a replacement tariff."
However, he suggested that bill-payers take a meter reading and email it to themselves with a timestamp.
He said: "Do not panic. Your credit is protected and you won't be locked in a new deal.
"Once you've switched across, you'll be able to shop around for a better tariff. But right now, you need to wait until Ofgem has found a replacement supplier."
Green Network Energy and Simplicity Energy are the latest failures in a sector that has been squeezed in recent years.
High-profile firms including Tonik, Breeze, Economy Energy, Solarplicity, and Spark Energy have also collapsed, leaving many households in limbo.
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Philippa Pickford, Ofgem's director of retail, said: "Green Network Energy and Simplicity Energy customers do not need to worry, as under our safety net we'll make sure your energy supplies are secure and domestic customers' credit balances are protected
"Ofgem will now choose a new supplier for you and whilst we are doing this our advice is to wait until we appoint a new supplier and do not switch in the meantime.
"You can rely on your energy supply as normal. We will update you when we have chosen a new supplier, who will then get in touch about your new tariff."
