Between them the two firms had about 35,500 domestic energy customers. The two firms both ceased trading last week, citing the surging price of wholesale gas as the reason.

The energy regulator appointed British Gas to take on the bust firms’ customers after a ‘competitive’ process to ‘get the best deal possible for customers’.

Funds that current and former domestic customers of both suppliers have paid into their accounts will be protected, where they are in credit. Domestic customers will also be protected by the energy price cap with their new supplier.

For existing Neon Reef and Social Energy Supply customers, energy supplies will continue as normal after they were switched over to British Gas on Sunday 21 November.

Customers of both suppliers will be contacted over the coming days about the changes. If customers wish to switch supplier, they can shop around but are advised to wait until the transfer has been completed. Customers will not be charged exit fees if they decide to switch to another supplier.

Neil Lawrence, Ofgem’s director of retail, said: “I am pleased to announce we have appointed British Gas for the customers of Neon Reef and Social Energy Supply. We understand that this news may be unsettling for customers, however they do not need to worry. Their energy supply will continue as normal, and customer credit balances will be honoured.

“Customers’ energy supply will not be interrupted and British Gas will be in contact with customers over the coming days with further information. Once the transfer has been completed, customers can shop around for another deal if they wish to.”

Yesterday saw the UK’s seventh largest energy supplier Bulb enter special administration after failing to find investors for the firm. Rumours of Bulb’s demise have been circulating for several weeks, following the collapse of more than 20 energy firms since August when wholesale energy prices started to rise to unprecedented levels.