UBS shares lost 2% after a study claimed that it could end up with an $8bn bill all in if it is found to have committed wrongdoing under the various regulatory probes across the world into suspicions of currency market rigging.
That would be the largest fine of all the banks currently under investigation over what may have gone on in the $5tn (£3.1tn, €3.7tn) daily currency markets, according to calculations by Autonomous Research.
Autonomous studies financial firms in the US and Europe. It is chaired by Lord Myners, the UK's former City minister under the Labour government.
If its estimates are correct, the UBS cost in fines and compensation alone would dwarf the $6bn paid out by all banks in the aftermath of the Libor-fixing scandal.
"We acknowledge that our methodology is speculative, but it applies the theory that repeated wrongdoing attracts higher penalties, as witnessed elsewhere," said the Autonomous report, after whose release UBS shares lost around 2% in early New York trading.
In March 2014, UBS suspended four of its foreign exchange traders in Singapore, Switzerland and New York. Many other banks, including Citi and HSBC, have also suspended staff amid the investigations.
The Swiss investment bank had set aside 1.7bn Swiss francs (£1.12bn) in 2013 for legal provisions. It has not commented on the speculative $8bn claim in the Autonomous research.
Regulators from the UK to the US, Hong Kong to Switzerland, have opened investigations into the global foreign exchange market.
Autonomous said the total bill for all banks could hit $35bn.
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