A British exit from the European Union will slash between 2 percent and 5 percent off the country's gross domestic product (GDP), according to Michael Browne, a fund manager at the London-based investment management firm Martin Currie.
Browne said that a so-called Brexit would cause the same level of economic damage to the U.K. as the recessions of 1991 and 2008, hitting consumers and further weaken overseas investment in a country that has seen some promising growth since the last financial crash.
"It wouldn't all happen overnight but that's the sort of cost level you are looking at. You are looking at rising inflation, weaker sterling, would interest rates have to go up? Would you see a movement away, let's say half a million people move out of the U.K., because they return home to get their jobs?," he told CNBC Tuesday.