Tan Chi Min, a former RBS derivatives trader, is suing the bank for wrongful dismissal—a case that Financial Times reports is rooted in the LIBOR scandal.

Read: How to reform LIBOR: CFA poll

Tan was fired in November 2011 for alleged gross misconduct relating to the setting of LIBOR. Now, he counters in his lawsuit that it was part of his duties to provide rate-setters for LIBOR with “input” and that RBS condoned the practice, reports Financial Times.

Bloomberg has reported court filings where Tan boasts to colleagues about how the firm was able to move global interest rates.

“Our six-month fixing moved the entire fixing, hahahah,” he says in an April 2008 instant message with traders including Neil Danziger, who also was fired by RBS, and David Pieri.

Read: LIBOR lesson: your boss reads your instant messages

RBS is disputing the allegations, and says it “continues to co-operate fully with ongoing investigations relating to the setting of LIBOR and other interest rates.”

The Singapore case comes just after BBA earlier this week bowed out of LIBOR.

Read: British banks step back from LIBOR