The Energy Ombudsman has revealed it opened investigations into 1,160 complaints regarding Extra Energy over the past 12 months.
Yesterday (21 November) it was announced the Birmingham-based supplier had ceased trading.
Ofgem said it will choose a new supplier to take on the company’s customers “as quickly as possible”.
Chief executive at the Energy Ombudsman, Matthew Vickers, said: “We are keen to work closely with whichever supplier is chosen to take on Extra Energy’s customers to help ensure a smooth transition for consumers, as we did with Octopus Energy following the collapse of Iresa in July.
“In the meantime, we would echo Ofgem’s advice to consumers, which is to sit tight, take a meter reading and resist any temptation to switch supplier.
“If you’re a consumer who has a complaint about Extra Energy open with us, please be advised that we will be in touch in due course with information on next steps.”
Ofgem has also proposed new financial and customer service tests for companies seeking a supply licence.