A vote to leave the European Union in a June 23 referendum could cost each Briton around 45,000 pounds ($65,718), or around half the value of the United Kingdom's housing stock, JPMorgan Chase & Co said in a research report.
Some financiers say a British exit would sap London's wealth, hammer sterling, undermine the world's fifth-largest economy and prompt some traders to move their business to other centres such as New York and Singapore.
Using the British finance ministry's central estimate that UK gross domestic product would be 6.2 percent lower by 2030 after a Brexit than it would be if Britain stayed in the EU, JPMorgan said the impact on British wealth could be huge.
"To make it personal, each individual's wealth would be lower than it would otherwise have been by around 45,000 pounds," JPMorgan said in the note for clients. "This is huge."
"To put it differently, the hit to wealth would be equivalent to a loss of around half of the value of the UK's housing stock and the land associated with it."
JPMorgan also projected the impact on wealth based on a group of Brexit-supporting economists who on Thursday forecast a British exit would benefit the economy.
Under that scenario, which sees a 4 percent boost for gross domestic product after around 10 years, each Briton would get a wealth boost of about 29,000 pounds, equivalent to about 40 percent of the UK housing stock, JPMorgan said.
The note did not mention a timeframe for the different estimates of changes to wealth.
JPMorgan, which has donated to the "In" campaign, did not say which scenario was most likely but noted the wide range of forecasts. The Organisation for Economic Co-operation and Development said this week that a Brexit would leave Britain's economy 5 percent smaller by 2030 than if it stayed in the EU. ($1 = 0.6847 pounds)