The battered pound may rally about 9 percent against the Swiss franc if Britain votes to remain in the European Union, according to UBS Wealth Management, which manages about $2 trillion.

A vote by Britain to exit the world's largest trading bloc has the potential to move the pound, which has slid 6.9 percent against the franc this year, down by a "decent amount" versus its Swiss peer, which would act as the "ultimate" haven in such a scenario, the Zurich-based wealth manager said.

The pound is trailing behind all its Group-of-10 major counterparts this year amid speculation a June 23 vote to quit the EU would set back the U.K.'s economic recovery, which would then keep the Bank of England from tightening monetary policy. The Federal Reserve started raising rates last year, and traders put the odds of another move before the July policy meeting at 51 percent, from 35 percent at the end of February.