Three more energy suppliers have collapsed under the weight of rising gas prices, taking the total number of failures to 12 this year and forcing the regulator, Ofgem, to find new suppliers for a further 233,000 customer accounts.

Ofgem said Igloo Energy, Symbio Energy and Enstroga had become the latest companies to succumb to a gathering crisis that shows no sign of abating, with gas prices remaining stubbornly high amid international shortages as winter approaches.

The regulator stressed that customers would not suffer disruption to the supply of energy to their homes, adding that anyone with credit in their accounts with those companies would not lose their money.

But it will now have to find a new energy provider for nearly a quarter of a million people via its “supplier of last resort” scheme, under which financially healthy companies take on the customers of their collapsed rivals.

Firms that take on new customers are later compensated for their costs via an industry-wide levy that is ultimately added to gas bills.

Earlier this week, Shell Energy took on 255,000 customers from a collapsed smaller rival, Green, while Octopus Energy has taken on 580,000 left stranded when Avro Energy failed.

Before the latest collapses, announced on Wednesday, the number of households supplied by an energy company that had gone bust this year totalled almost 2m, forcing Ofgem into an unprecedented scramble to keep to the customer transfer system going.

Neil Lawrence, the director of retail at Ofgem, said: “We know this is a worrying time for many people and news of a supplier going out of business can be unsettling.

“I want to reassure customers of Enstroga, Igloo Energy and Symbio Energy that they do not need to worry. Under our safety net we’ll make sure your energy supplies continue. If you have credit on your Enstroga, Igloo Energy or Symbio Energy account, the funds you have paid in are protected and you will not lose the money that is owed to you.

“Ofgem will choose a new supplier for you and while we are doing this our advice is to wait until we appoint a new supplier and do not switch in the meantime.

“You can rely on your energy supply as normal. We will update you when we have chosen a new supplier, who will then get in touch about your tariff. Any customer worried about paying their energy bill should contact their supplier to access the range of support that is available.”

Igloo Energy is the largest of the companies that went under on Wednesday, with 179,000 customers, followed by Symbio with 48,000 and Enstroga with 6,000.