Tyneside-based energy supplier Future Energy has ceased trading, the industry regulator has confirmed.
The Newcastle company, which was set up in 2014, had about 10,000 domestic customers - mainly in north-east England - and employed 50 staff.
Ofgem said it had stepped in to secure supplies and would appoint another company to take on existing customers as soon as possible.
No-one from Future Energy was available for comment.
A spokesman for Ofgem said: "Customers of Future Energy will have their energy supply continue as normal, and their outstanding credit balances will be protected.
"If you are a customer of Future Energy there is no need to worry."
He said the new supplier would contact customers once it had been chosen.
At the time of the company's launch, managing director Tim Cantle-Jones said he hoped to poach at least 80,000 customers from the UK's "big six" energy suppliers.