The news comes after the company, which supplied less than 100,000 households, was banned from taking on new customers after it failed to resolve its customer service problems.
It was also branded the “worst energy company” for customer service by Citizens Advice amid record complaint levels.
This is to ensure the process of handing customers to the new supplier and paying back their outstanding credit balances is hassle free.
Rob Salter-Church, Ofgem’s Interim Executive Director for Consumers and Markets said: “If you are an Iresa customer, there is no need to worry as we will make sure your energy supplies are secure and your credit balance is protected.
“Ofgem is working to choose a new supplier as quickly as possible for you. Whilst we’re doing this, our advice is to ‘sit tight’ and don’t switch. Your energy supply will not be affected and will continue as normal – the thing that will change is that your energy will come from a new supplier.”
Last month, the regulator launched a review to tighten up checks for new entrant energy suppliers.