The Bank of England believes 75,000 jobs will leave the City on Brexit.
The central bank argues the figure is a likely scenario if the UK and the European Union do not agree to a specific financial services deal, the BBC reports.
EU chief negotiator Michel Barnier has previously said there will be no bespoke deal for the City.
Brexit minister David Davis has said the UK will not be part of the single market or customs union meaning any trade agreement is likely to focus on goods over services.
The Bank of England reckons 10,000 jobs will leave on day one of Brexit, with most expected to leave within the next five years.
However, it says there are opportunities from Brexit such as providing financial services for emerging markets across the Middle East and Asia including China and India.