Biggest banks face forex probe questions

Daniel Schäfer and Caroline Binham
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The global probe into foreign exchange manipulation has widened to include 15 of the world's biggest banks and some of the most actively traded currencies, as lenders scramble to help authorities in exchange for leniency.

The UK's Financial Conduct Authority – one of seven regulators handling the worldwide investigation – has in so far requested information from at least 15 banks, according to two people close to the situation. The rapidly accelerating probe is looking at whether traders manipulated markets by sharing information and trading ahead of their clients.

(Read more: EU to fine banks billions of euros over rate rigging)

Investigations by the FCA as well as authorities in Switzerland, the US and Hong Kong are focusing on the euro-dollar market, the most liquid currency market in the world which accounts for almost a quarter of the $5.3 trillion daily trading volume.

Regulators and banks are also scrutinizing trading in , Australian dollar and Scandinavian currencies, two people familiar with the situation said, pushing the probe well beyond the niche currency markets that were initially thought to be under review.

European banks' return on equity is weak
European banks' return on equity is weak

Joaquín Almunia, the European Union competition commissioner, said that several banks have handed over information to Brussels to assist it with its antitrust inquiries in the hope of winning leniency.

He said the commission would start directing more resources to the foreign exchange investigation once it had finished settling with banks who were involved in the Libor scandal, which he said had cast a shadow over "thousands of financial benchmarks".

"Before Libor, people thought benchmarks could be trusted. Now there's a presumption that there's a risk of manipulation. Perhaps manipulation is not the exception but the rule."

(Read more: Banks and trust: No honor system here)

Banks have completed lengthy inquiries into whether traders rigged Libor and other benchmarks, but the global investigation into currency manipulation was sparked by a whistleblower, who approached the FCA with their concerns, several people familiar with the investigation said.

UK authorities have been looking foreign exchange markets for at least two years amid widespread suspicions among investors and market participants about possible manipulation of a crucial benchmark, the 4pm WM/Reuters fix.

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But their concerns were repeatedly dispelled by senior traders and reviews by banks and authorities did not yield any results before this spring.

Authorities have started examining trading connected to an array of financial benchmarks after the Libor interbank lending rate scandal erupted in full force last year, so far prompting more than $3.5 billion in fines against financial institutions.

The banks under investigation by the FCA and other regulators in the sprawling currencies probe include Barclays, Citigroup, Deutsche Bank, Goldman Sachs, HSBC, JPMorgan, Morgan Stanley, Royal Bank of Scotland, Standard Chartered and UBS. All of those banks – and a number of others – have launched internal reviews.

Bankers have long claimed that the foreign exchange market is impossible to manipulate given its vast size, but the investigation's focus on the most liquid currencies such as the euro undermines this argument.

(Read more: UK to toughen London share listing rules)

A currency manager at a large asset manager said that despite the foreign exchange market's liquidity, an order of some $200 million or less would often be large enough to influence prices.