Credit Suisse Group AG senior adviser Bob Parker warned that about 45,000 jobs in the City of London could be at risk if Britain votes to leave the European Union.

“The City of London, I think, would be challenged on a Brexit,” he said in an interview with Anna Edwards, Guy Johnson and Manus Cranny on Bloomberg Television on Wednesday. About 300,000 people are employed in the U.K. capital’s financial district and “it’s not an unrealistic forecast to say that the job losses with a Brexit could be perhaps 15 percent of that number,” he said.

Senior financiers have predicted a U.K. vote to leave the 28 member trading bloc in a June 23 referendum would threaten London’s status as a global business hub and drive firms from banks to asset managers to relocate jobs. HSBC Holdings Plc Chief Executive Officer Stuart Gulliver has said he would move about 1,000 investment bankers to Paris, while ING Groep NV CEO Ralph Hamers has said the Dutch lender would probably follow other major banks in reducing its staffing levels.

BlackRock Inc., the world’s largest money manager, said in a report sent to clients this week that the U.K. would generate lower economic growth and suffer a drop in investment if voters decide to leave the EU. Vice Chairman Philipp Hildebrand said a Brexit “offers a lot of risk with little obvious reward.”