Canary Wharf property boss Sir George Iacobescu has said London would be overtaken by other key European cities within five years if Britain leaves the European Union.
"There is nothing you have here in London that is not replicable," Iacobescu said at the City Property Association's EU referendum debate last night.
"Whether it is Frankfurt or Paris, the Germans, French and Spanish would be able to catch up in three to four years, not 20 as some [on this panel tonight] have suggested."
His comments were quickly dismissed by the Vote Leave campaign.
"London is the financial capital of the world," a Vote Leave spokesman told City A.M. "It is empowered by its tax system, its global talent pool and the infrastructure already here.
"If Paris and Frankfurt were such enviable markets, they'd be doing far better than they already are."
Iacobescu was a signatory of the February letter signed by almost 200 business leaders that called for Britain to remain in Europe.