UBS, the world’s biggest wealth management firm, has issued a worldwide travel ban for its managers of wealthy clients as the bank continues to wrestle with a high-profile tax evasion civil lawsuit in the US.

UBS managers who handle clients from countries other than Switzerland are barred from going overseas, a UBS spokesman confirmed to WealthBriefing.

The travel ban affected the Swiss bank's international business with all countries, he said. Swiss newspaper Sonntags Blick reported on Sunday that more than 1,000 employees would be affected by the ban.

UBS is assessing the guidelines and rules of behaviour related to its international asset management business, the bank said.

The bank has provided US tax authorities with the details of 255 wealthy US nationals suspected of tax fraud in connection with a recent criminal case, but refused to identify about 50,000 more US account holders Washington wants as part of a civil action against the Swiss bank.

UBS has already moved to stop providing offshore banking services to US clients.

Last month, it was reported that Switzerland’s private banks have started to ban their top executives from travelling abroad, even to neighbouring France and Germany, because of fears they will be detained as part of a global crackdown on bank secrecy.

However, the Swiss Banking Association has not recommended that its members refrain from foreign travel abroad although individual banks, however, are obviously free to choose their own approach, Pierre Mirabaud, association chairman, has said.