Mr Dennis is suing 17 international banks, including the big four Australian banks, for allegedly rigging the bank bill swap rate from 2003 onwards. Mr Dennis was a purchaser of products that were based on that rate and alleges he lost million from the rate rigging.

The bank bill swap rate, or the BBSW, is one of the most important interest rates in the economy and helps set the interest rates on loans to large corporate entities.

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Westpac Banking Corporation, National Australia Bank, ANZ Banking Group and Commonwealth Bank were individually sued by the Australian Securities and Investments Commission which alleged each bank had rigged or attempted to rig the bank bill swap rate for their own financial benefit.

NAB, ANZ, and CBA settled the case, with NAB and ANZ each handing over about $50 million and CBA $25 million after admitting to attempting to rig the rate. Westpac was later found to have engaged in unconscionable conduct for its alleged attempts at rate rigging.

The Australian banks have been vigorously defending the New York class action.

In a letter to the court in New York, lawyers for Mr Dennis and OCEF said the settlement was an "ice breaker" and included "non-monetary cooperation".

“JPMorgan’s documentary cooperation will include what the plaintiffs understand to be millions of pages of documents previously produced by JPMorgan to government investigators, as well as data relating to loans, trades, and other transactions involving the Australian bank bill swap reference rate (“BBSW”) markets at issue in this action,”

The plaintiffs said they agreed to settle with JPMorgan because unlike other banks they are suing, JPMorgan was not subject to any sanction in Australia, but said the bank was in a position to provide evidence against its rivals.

“Moreover, JPMorgan entirely denies any and all wrongdoing in the BBSW market. Plaintiffs have alleged that JPMorgan did participate in the agreement by assisting other defendants."

NAB, ANZ, CBA and Westpac declined to comment.