LONDON - A third of the staff of the Singapore office of RBS Coutts, a private bank that is part of the Royal Bank of Scotland Group Plc (RBS), have quit in a mass resignation, the bank said on Tuesday.

A spokesman for RBS confirmed a story in the Financial Times that 20 key managers resigned along with around 50 support staff in a move the newspaper said could be related to bonus prospects.

RBS was rescued by the British government last year and its bonus payments to staff have been under careful scrutiny.

The RBS spokesman said the resignations represented less than 15 percent of the regional headcount.

"Staff volatility in the private banking industry is not unusual, especially in Asia," the spokesman said.

He declined to comment on the reason for the resignations.

(Reporting by Christopher Johnson; editing by Andre Grenon)

-Reuters