The London mayor has this morning published an analysis of a worst-case Brexit scenario, and what it would mean for the capital. The paper is a response to the government's failure to produce its assessment on how Brexit would impact the economy.
The analysis, which was carried out by Cambridge Econometrics, found that investment into the UK could fall by as much as £50bn.
The sector taking the biggest hit would be financial and professional services, with UK job losses potentially reaching 119,000.
The mayor said the analysis showed the government should keep the UK in the Single Market and the customs union.
“If the government continue to mishandle the negotiations we could be heading for a lost decade of lower growth and lower employment," said Khan.
“The analysis concludes that the harder the Brexit we end up with, the bigger the potential impact on jobs, growth and living standards. Ministers are fast running out of time to turn the negotiations around. A “no deal” hard Brexit is still a very real risk – the worst possible scenario."
The report comes after the City of London said job losses in financial services may be lower than previously estimated.
Jeremy Browne, the City of London Corporation's EU envoy, said plans to move jobs out of the UK were becoming less drastic, with large banks and insurers saying they will not abandon London after Brexit.
Consultants Oliver Wyman estimated that the City could face job losses numbering 75,000, but more recently, the Bank of England said it was assuming 10,000 "day one" job losses after March 2019.