Citibank's International Personal Bank has temporarily closed its doors to new UK business while the Financial Services Authority runs the rule over its anti-money laundering procedures.
The unit, which caters to 170,000 affluent customers globally, has frozen new account openings in the UK after an internal review uncovered "process and resource" issues in its AML systems.
The failings have been flagged with the UK regulator and the bank has been asked to provide the FSA with weekly updates until the problems have been resolved. The watchdog is also expected to appoint an independent third party to review CIPB's systems.
In a statement, Citi says: "The business has grown 70 percent over the last 12 months and is taking a pause with regard to new accounts while we ensure adequate resources are in place. It is business as usual for all existing customers. This is a process and resource issue."
A spokesperson says the decision to temporarily suspend new account openings was made by Citi.