Soaring energy bills could be the "straw that finally breaks the camel's back" for small businesses, former chancellor Alistair Darling has warned.
Mr Darling, who was Labour chancellor during the financial crisis, said "bold action" was needed to help the economy.
The energy price cap for households will soar by 80% from October.
But firms are not covered by the cap and Mr Darling said that after surviving Covid, energy costs risked finishing them off.
Mr Darling described the current situation as a "lethal cocktail" and said it required "bold action" to be taken by the government.
Both candidates in the Conservative Party leadership race, Liz Truss and Rishi Sunak, have come under pressure to outline further support for households and firms following the announcement that energy bills would rise again this Autumn.
The new leader - and prime minster to succeed Boris Johnson - will be announced next Monday.