Commonwealth Bank is reviewing its membership of two interest rate panels in the Libor market following National Australia Bank's decision to withdraw from the scandal-ridden system.CBA is the only Australian bank participating in the Libor market, through its membership of panels that set inter-bank rates for loans denominated in Australian and New Zealand currencies.While international regulators investigating rigged bids and insider trading within the Libor system have not turned the spotlight on either of these benchmarks, the reputation of the A$ and $NZ panels may nevertheless have been tainted by the involvement of global banks tied to the manipulation of Libor benchmarks in other currencies.Three of the banks at the centre of the investigations into the manipulation of Libor benchmarks in North American and European currencies - Barclays, Deutsche Bank and the Royal Bank of Scotland - are active members of the A$ and $NZ panels. The British Bankers Association is responsible for the operation of the panels.In June, Barclays was fined £290 million by US and UK authorities after it conceded that staff and executives had submitted "false" and "knowingly inaccurate" bids in the Libor process since 2005.In July, Deutsche Bank admitted that some of its employees had been involved in rate rigging.CBA spokesman Steve Batten refused to comment on whether any CBA staff had been asked to co-operate with the regulatory inquiries but insisted that the bank was not under investigation.  He also declined to comment on when the bank would announce a decision on whether to renew its membership of the Libor panels."Commonwealth Bank does not comment on strategic matters. However, Commonwealth Bank has been on this panel for a number of years," he told Banking Day in an email, in response to questions."And to clarify, we are not being investigated."One of the early signs that the Libor panel system was rotten came in October last year, when the European Commission raided the offices of 15 banks in London and other European cities. While these raids related to suspicious activity around the setting of another benchmark rate - the European Inter Bank Offered Rate - they sent a strong signal to the global banking industry that the US and British investigations into Libor had merit.A few weeks after these raids, National Australia Bank quietly ended its 22-year involvement in the Libor A$ panel.Although the Libor A$ benchmark had never been the main reference rate for NAB's Australian dollar funding during its long involvement on the panel, the bank's spokeswoman, Fiona Macrae, said this was the rationale for the bank's withdrawal from the A$ panel."As NAB's A$ debt instruments settle off BBSW, not Libor, NAB decided there was no value or business requirement to remain on the committee," Macrae said."Following the 2011 annual committee review, NAB took a decision to discontinue membership of the committee."  Few borrowing contracts reference the A$ Libor rate. Recent work by the Reserve Bank of Australia to establish the importance or otherwise of this benchmark turned up only a score or so of