Selkirk-based Spark Energy Supply Limited has been closed down by its parent company. It had 290,000 domestic customers.
Other businesses within the Spark Group, such as Spark Business Utilities, which serves commercial customers, remain trading. The company also operates gas shipping, energy finance and home telecom subsidiary businesses.
Earlier this week the company was named by regulator, Ofgem, as one of two firms it investigating over unpaid Renewables Obligation buyout payments, which suppliers are obliged to pay if they do not buy a certain amount of power from renewable sources.
Some £59m is missing and other suppliers will have to find the money or potentially, also go bust.