Morgan Stanley has disclosed that up to 10 per cent of its wealth management clients had their account information stolen by an employee who may have been looking to sell it.

The bank, which operates one of the largest wealth management operations in the US, said an employee from that division - who it did not name - had “briefly” published to the internet the account names and numbers of about 900 of those clients.

The employee was fired and the incident reported to law enforcement and regulators, Morgan Stanley said, adding that there was “no evidence of any economic loss to any client”.

“The data stolen does not include account passwords or social security numbers,” the bank stressed in a statement. “The firm is taking the precaution of notifying all potentially affected clients and instituting enhanced security procedures including fraud monitoring on these accounts.”

Shares in Morgan Stanley fell 3.2 per cent by mid-morning, outpacing declines in other US bank stocks.

Morgan Stanley discovered the published account information on December 27 during routine scans of the internet, according to a person familiar with the matter, who said it had received “virtually no hits”.

“Morgan Stanley takes extremely seriously its responsibility to safeguard client data, and is working with the appropriate authorities to conduct and conclude a thorough investigation of this incident,” the bank said.

(c) 2015 The Financial Times Ltd.