Royal Bank of Scotland pulled out of a Singapore panel setting interbank lending rates.
People at other banks also said they might seek to get out of the panels, which set daily rates such as the London interbank offered rate, a benchmark underlying anything from mortgages to complex derivatives.
Partaking in the panels was once deemed a prestigious task, but is now tainted with the suspicion of manipulation, particularly so for smaller, less liquid currencies.
RBS has already exited panels in Tokyo and Hong Kong, the Financial Times reported earlier this month.
An investigation into manipulation of London interbank lending rates started late last year and seized headlines last month when Barclays paid a $453 million fine to settle with U.S. and UK regulators over its role in rate fixing.
More than a dozen other banks are involved in the probe, which has thrown the spotlight on the discredited process for setting the rates that are the basis for hundreds of trillions worth of financial contracts.
"During the course of this review, we have decided to end our contribution to the rate setting panels for Sibor in Singapore," said RBS Spokeswoman Patricia Choo.
"What has emerged from this in terms of policy suggestions is that any rate which is based on estimates rather than actual financial transactions is highly dubious," said Justin O'Brien, director of the centre for law, markets and regulation at the University of New South Wales in Sydney.
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