Rishi Sunak was last night racing to plug "gaps" in his latest support package for businesses and workers, as he faces claims that he has "left behind" the self-employed.

The Chancellor is "actively considering" possible ways to broaden the scope of measures announced on Friday, which included paying up to 80 per cent of individual employees' wages.

He is being lobbied to mirror the approach of Norway, where the government is to pay self-employed workers grants equating to 80 per cent of their average income over the past three years. Mr Sunak is also under pressure to announce major additional support for airports and airlines.

More than 2,000 musicians have signed a letter to Mr Sunak warning that the Covid-19 outbreak has resulted in the "complete shutdown of our places of work." Equity, the actors' union, separately warned that "no one should be left behind just because their employment is insecure". Taxi drivers also said they were "effectively unemployed".

The letter, whose signatories include musicians from the London Symphony Orchestra and a series of West End musicals, states: "We are deeply concerned about the difference in treatment between the employed and the self-employed."

The musicians, led by Ed Barker, a former Tory candidate and sax soloist for George Michael, added: "We are not asking for special treatment, we are simply asking for fair and equal treatment and for the Coronavirus Job Retention Scheme to be extended to the self-employed."

A Treasury spokesman said self-employed workers would already "benefit from a relaxation of the earnings rules for self-employed claimants under universal credit and deferring income tax self-assessment payments due in July 2020."

She added: "We have always said we will go further where we can and are actively considering further steps.”