Alleged poaching of staff from Credit Suisse's private bank in the US by UBS has led to a legal challenge, a report says.

Credit Suisse has filed an arbitration claim with a US regulator claiming that a unit of rival Swiss bank UBS unfairly poached staff from its US private banking arm, according to the Wall Street Journal.

The article quoted unnamed sources. UBS declined to comment; this publication is in contact with Credit Suisse and may update in due course.

The WSJ said the claim was filed with the Financial Industry Regulatory Authority.

The claim was placed as Credit Suisse winds down the US unit at which the financial advisors worked. About 70 of the 300 brokers from that division have left for UBS in recent months, the newspaper said.

A UBS spokesperson reportedly declined to comment to the WSJ; a FINRA spokesperson also declined comment. The publication said Credit Suisse could not be immediately contacted.

The report said the departures of Credit Suisse staff to its rival Swiss bank hurt a plan to transfer US private-banking business from Credit Suisse to Wells Fargo & Co.