"If the outcome of the referendum is to exit, what you have for sure is going to be two-to-three years of intense negotiation and a massive uncertainty and that will really affect the UK economy substantially and the European economy," Daniel Pinto said during a presentation at the bank's annual investor day in New York on Tuesday.

For JPMorgan, the impact of a vote for so-called 'Brexit' could range from moving "a few hundred salespeople" to being forced to "duplicate the whole infrastructure" JPMorgan has in the country to a location within what remains of the European Union, Pinto said.

The second scenario would be "extremely costly" and "will be real tough for everyone else," Pinto said.

Pinto added that the outcome of Britain leaving the European Union "may be good or bad in the long term. In the short term, the amount of uncertainty based on the negotiations will be really bad for everyone."

(Reporting by Dan Freed; Editing by Bill Rigby)

By Dan Freed