Pedestrians are reflected in the window of a branch of the Royal Bank of Scotland in London. Picture: Suzanne Plunkett

London - Royal Bank of Scotland traders laughed as they manipulated Libor interest rates and dubbed the market a cartel, according to emails published by regulators on Wednesday.

“Our 6m fixing move the entire fixing, hahaha,” a Japanese yen derivatives trader boasted to another trader, according to documents released by British and US regulators on Wednesday.

In another exchange in August 2007, a senior RBS yen trader said: “Its just amazing how libor fixing can make you that much money ... it's a cartel now in london.”

RBS is paying $615 million to US and British authorities to settle allegations it manipulated Libor, making it the third bank to be fined for rigging the benchmark rate.

The revelation of dozens of emails sent by traders at RBS to colleagues and traders at other banks are an echo of the embarrassing emails and messages seen at Barclays and UBS when they settled Libor manipulation cases last year.

They have been seized on by politicians and an angry public as evidence of a brazen attitude to fixing prices, with traders calling each other “superman” or “a hero” for the manipulation, and promising rewards or praising each other.

Britain's financial regulator said at RBS improper requests for Libor submissions occurred between 2006 and 2010. It involved three benchmark rates and at least 21 derivatives traders and primary submitters, mainly in London and Tokyo and also in the United States and Singapore. - Reuters