Credit Suisse staff had already been seeking to jump ship in recent weeks, sources told Reuters.
"Many Credit Suisse bankers had already been talking to a lot of people for a while [about leaving the Swiss bank].
An executive at a rival London-based wealth manager said they had seen a steady flow of CVs coming in from Credit Suisse bankers.
UBS told Credit Suisse wealth bankers on Monday that it was weighing financial sweeteners for them to stay, as it seeks to reassure key staff.
Some experts have said Britain's financial services industry could ultimately benefit from recent bouts of turmoil in the United States and Switzerland.