By Caroline Binham, Brooke Masters and Megan Murphy in London

Almost a dozen traders and brokers in London and Asia have been fired, suspended or put on leave by their employers as a multinational probe into alleged manipulation of crucial global lending rates accelerates.

Regulators have been investigating US and European banks that help set interbank lending rates in London and Tokyo since late 2010, in an intensive inquiry that spans three continents and involves at least nine enforcement agencies.

In the past few months, officials have also expanded their inquiries to hedge funds that place big bets on movements in those rates and the interdealer

brokers that serve as go- betweens with the banks, according to people familiar with the probe.

Icap, the world?s largest interdealer broker, has suspended one employee and put two more on leave in the past six weeks. Icap said only that it was ?co-operating fully? with authorities.

According to people familiar with the probe, traders have also been suspended or fired in recent months at JPMorgan Chase, Royal Bank of Scotland and

Citigroup. All three banks declined to comment.

Regulators are seeking to determine whether banks colluded to set the overnight lending rates known as Libor, Tibor and Euribor, and whether traders within the banks and their clients improperly used information on what future rates would be to place profitable trades. The rates, which serve as a benchmark for $3.5tn worth of financial products worldwide, are set by a daily poll of a panel of banks in each region.

A statement published by Switzerland?s Competition Commission last week said: ?Derivative traders working for a number of financial institutions might have manipulated these submissions by co-ordinating their behaviour, thereby influencing these reference rates in their favour.

?Moreover, derivative traders might have colluded to manipulate the difference between the ask price and the bid price [spread] of derivatives based on these reference rates to the detriment of their clients.?

US and UK regulators have sought information from the three London-based interdealer brokers that dominate the rates market – Icap, Tullett Prebon and RP Martin. People familiar with the matter said they were looking at information-sharing among brokers, hedge funds and banks.

An RP Martin spokesman said the firm was not under investigation and declined to comment on suspensions. Tullett Prebon said the firm had not suspended any employees.

With additional reporting by Kara Scannell in New York,

Michiyo Nakamoto in Tokyo, and Paul J. Davies in Hong Kong

? The Financial Times Limited 2012