Citigroup has been ordered to pay $10.75 million to a former customer over losses from investments in Royal Bank of Scotland Group, the UK-listed bank which has been partly owned by the UK taxpayer since the 2008 financial crash, media reports said. (RBS last week reported a profit for the second quarter of 2013.)

The US Financial Industry Regulatory Authority arbitration panel also ordered Edward Mulcahy, a former Citigroup broker, to pay $250,000 to the investor, John Leopoldo Fiorilla, according to a July 30 ruling.

"We are disappointed with the award, which was not supported by the facts," a Citigroup spokesperson was quoted by Reuters as saying.

This publication was unable to reach Citigroup for further information as at the time of going to press.

Fiorilla filed the case in 2010, seeking $19.5 million in damages, according to the ruling. Citigroup, he alleged, was grossly negligent and failed to supervise its broker. Mulcahy left Citigroup in 2009. He recently retired from Morgan Stanley. Efforts to locate him were not successful, Reuters said.