Measures suggested by the Mayor in the letter include improved access to business support grants; the introduction of a rent support scheme; and further funding to London to 'safeguard the small business ecosystem'.
"The Government’s unprecedented business support package has helped many businesses survive the lockdown so far and, as you know, I support the Government in these actions," says Khan.
"However, I have concerns, shared by business groups across the capital, that many London firms will need additional and ongoing support to survive the continuing lockdown and the exit and recovery periods which will follow."
In support of the #RaisetheBar campaign, the Mayor asks the Chancellor and Business Secretary to raise the rateable value threshold for Retail, Hospitality and Leisure Grants from £51,000 to £150,000.
Under the current grant scheme, business with a property that has a rateable value of up to £15,000 will receive a grant of £10,000; while those with a property that has a rateable value of between £15,000 and less than £51,000 will receive a grant of £25,00.
"Nearly 30,000 struggling London businesses would have received grants if they were located anywhere else in the country," he says.
"Even with the support of the Government’s recently announced Bounce Back Loans scheme, many will feel unable to take on debt for the lost income they will never recover."
Similarly to many voices across both the industry, and the political spectrum, the Mayor also asks for amendments to be made the Coronavirus Job Retention Scheme (JRS).
He asks the Government to support struggling businesses in the months ahead by allowing them to 'part-furlough' workers on reduced hours during lower demand periods; and to support lower-paid workers who have seen their income fall below the National Living Wage.
The Mayor previously championed his support for SMEs in the capital last month by launching a crowdfunding initiative aimed at supporting businesses across a variety of sectors, including hospitality.