Igloo Energy supplies gas and electricity to around 179,000 domestic customers, Symbio supplies around 48,000 domestic customers and a small number of non-domestic customers and Enstroga supplies around 6,000 domestic customers.
Under Ofgem’s safety net, the energy supply to all affected customers will continue and credit balances will be protected.
Domestic customers will also be protected by the energy price cap when being switched to a new supplier.
Customers of Enstroga, Igloo Energy and Symbio Energy will be contacted by their new supplier, which will be chosen by Ofgem.
Ofgem advised customers of the three firms to wait until a new supplier has been appointed and has made contact before looking to switch and to take a meter reading.
The three firms are the latest to collapse in recent weeks amid an unprecedented increase in global gas prices.
This means that nine small UK energy suppliers have gone bust since the start of September.
It comes after failures by People’s Energy, Green Supplier Ltd, Utility Point, PfP Energy, MoneyPlus Energy, and Avro Energy.
Ofgem said it was working closely with the Government and industry to make sure customers continued to be protected this winter.
Neil Lawrence, director of retail at Ofgem, said: “Ofgem’s number one priority is to protect customers. We know this is a worrying time for many people and news of a supplier going out of business can be unsettling.
“I want to reassure customers of Enstroga, Igloo Energy and Symbio Energy that they do not need to worry. Under our safety net we’ll make sure your energy supplies continue. If you have credit on your Enstroga, Igloo Energy or Symbio Energy account, the funds you have paid in are protected and you will not lose the money that is owed to you.
“Ofgem will choose a new supplier for you, and while 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 tariff.
“Any customer worried about paying their energy bill should contact their supplier to access the range of support that is available.”