It also found that under all scenarios London and the rest of the United Kingdom would keep growing, but more slowly than if the country had stayed in the EU.
The study by Cambridge Econometrics suggested that the capital's economy performs more strongly than other areas of the country in each Brexit scenario.
The analysis shows that under the worst of the five scenarios modelled - leaving in March 2019 without a deal or transition arrangements in place - would see 482,000 fewer jobs across the country and a loss of £46.8bn in investment by 2030.
"The introduction of WTO tariffs and a devaluation of the pound in case of a hard Brexit would shrink vehicle sales and manufacturing in the United Kingdom, directly impacting German auto suppliers", the report said.
Around 10,000 finance jobs will be shifted out of Britain or created overseas in the next few years if the country is denied access to Europe's single market, according to a Reuters survey of firms employing the bulk of workers in global finance.
As part of the study, five scenarios were examined, from the United Kingdom remaining in the single market and customs union, to leaving both, failing to get a free trade agreement or a transition period, and invoking World Trade Organisation rules.
Under a deal in which Britain was able to secure privileged access to the single market, annual growth...
The scenario that largely now fits the direction of travel is number four, which envisages a two-year transition period, before leaving the single market and customs union and falling back on WTO rules.
Britain's exit from the single market could mean these companies lose financial "passporting" rights that allow them to offer products and services on the continent from regional headquarters in the UK.
A Brexit deal with the European Union would result in only marginally lower United Kingdom growth and employment, an analysis commissioned by Sadiq Khan has concluded.
Trade negotiations between the United Kingdom and the EU are expected to resume in March, after the European Commission noted "sufficient progress" on three key issues: Northern Ireland, EU citizens, and the so-called "divorce bill".
"If the government continue to mishandle the negotiations we could be heading for a lost decade of lower growth and lower employment", said Khan.
Brexit was the main reason for a 37pc drop in new jobs available in London's financial sector last month, according to a separate report from recruiting firm Morgan McKinley.