British energy supplier Bulb expects to appoint administrators shortly, it said on Monday, becoming the biggest UK energy supplier so far to run into trouble since the recent surge in wholesale gas and electricity prices.
More than 20 energy suppliers have collapsed since the beginning of September, unable to pass on rising costs to customers because of the regulator Ofgem's price cap.
London-based Bulb, with more than 1.7 million customers, or around 5-6% of the market, had been in talks with multiple parties but failed to secure funding.
"The rising energy crisis ... has concerned investors who can't go ahead while wholesale prices are so high and the price cap - designed to protect customers - currently means suppliers provide energy at a significant loss," Bulb said in a statement on its website.
Analysts have said the difference between what companies can charge a customer under the cap and the current cost of supplying them with power from the wholesale markets is around 400 pounds ($538).
Britain's domestic price cap rose 12%-13% from Oct. 1 but wholesale prices have risen far higher since that cap was set in August.
Bulb said its international businesses in France, Spain and Texas were separate from the UK business and would continue to trade.