Neon Energy and Social Energy Supply have ceased trading, leaving 35,000 stranded customers in need of rescue from Ofgem.
Skyrocketing wholesale prices have now caused 21 firms to collapse since September.
The energy crisis has caused the number of suppliers UK market to halve as firms struggle to make up the costs.
Neon Energy is home to around 30,000 domestic electricity customers and Social Energy Supply has around 5,500 domestic customers.
Ofgem will designate a new supplier through its last resort process.
Domestic consumers will also continue to be protected by the £1,277 per year price cap when they switch.
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.
In total, over two million UK households have now been affected by supplier failures.