Energy bills will rise by as much as £85 next year following a raft of supplier collapses, the regulator has warned.

More than 20 energy companies have failed this year as the government-imposed price gap prevented them from passing on rocketing wholesale gas prices. Some 3.8m households have been affected, or 13pc of the market.

Ofgem appointed a “supplier of last resort” for the collapsed suppliers, meaning their customers have been moved to a competitor to maintain their electricity and gas supply.

The costs associated with taking on these customers will add between £80 and £85 to household bills, the regulator estimated.

However, an Ofgem spokesman said the figure should be “treated with caution”.

“It will continue to move up and down into next year as global gas prices remain volatile. We’re continuing to work with government and consumer groups to keep costs on customers’ bills as manageable as possible,” he said. 

The figure would be even higher if it included the cost of managing the collapse of Bulb Energy, which had 1.7m customers and is the largest failure so far. 

Last week Ofgem was forced to put the seventh-biggest supplier into “special administration”, the first time that has happened, while the Government has set aside £1.7bn to keep it going.