One of the most senior private bankers at UBS, the world’s leading wealth manager, has been detained by authorities in the US investigating whether the Swiss bank helped its American clients evade tax.

Martin Liechti, the Zurich-based head of North and South America for UBS’s international wealth management business, was held in connection with a US justice department investigation into investment advice that UBS gave its American private banking clients between 2000 and 2007.