Energy supplier EDF has taken on hundreds of thousands of Utility Point customers following the collapse of the smaller, Dorset-based supplier.
Watchdog Ofgem said it appointed EDF following a competitive process that would make sure customers were given the "best deal possible".
EDF started supplying all 220,000 Utility Point's domestic customers on September 18.
Utility Point said on its website that former and current customers’ credit balances were protected and EDF would contact users if necessary to determine the amount of any outstanding balance.
It said customers in debit to Utility Point should wait to hear from EDF or Utility Point’s administrators who would talk to them about repayment arrangements.
According to Ofgem, Utility Point customers will be contacted about the changes. They are being advised by the regulator to wait until the transfer has been completed before switching. People will not be charged exit fees if they decide to switch, however.
Ofgem also said EDF would be in touch with Utility Point customers with direct debits to explain how to set up an account. The watchdog is advising customers not to cancel their direct debits, which will be transferred by EDF.
Neil Lawrence, Ofgem’s director of retail, said: “I am pleased to announce we have appointed EDF as the new supplier for customers after Utility Point entered insolvency.
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"We understand that this news may be unsettling for customers, however they do not need to worry. Their energy supply will continue as normal, and all customer credit balances held on their accounts will be protected by EDF.
“Your energy supply will not be interrupted. EDF will be in contact with customers next week with next steps. Once transferred to EDF, customers can ask to be put onto another tariff, but should customers wish to switch, we advise waiting for the transfer from Utility Point to be completed.
"For answers to common questions you can read the FAQs on their website."
The news comes as Prime Minister Boris Johnson said the 海角视频 government would "do everything we can” to prevent energy companies going under as wholesale gas prices surge.
OG海角视频, representing the offshore oil and gas industry, reported wholesale prices for gas have surged 250% since January – with a 70% rise since August alone.
The rise in gas prices has been blamed on a number of factors, including a cold winter which left stocks depleted, high demand for liquefied natural gas from Asia and a reduction in supplies from Russia.
It comes as Business Secretary Kwasi Kwarteng is due to hold a fresh round of crisis talks with the energy industry, following the collapse of a number of suppliers.