The European Union has fined six finance groups a record 1.7 billion euros ($A2.55 billion) for rigging the Euribor and Japanese yen Tibor interest rates.
German Deutsche Bank, involved in rigging both rates, was fined a total of 725 million euros, and French bank Societe Generale was fined 446 million euros for manipulating the European Euribor rate.
Royal Bank of Scotland (RBS), already mired in controversy, was fined 391 million euros for involvement in cartels which rigged both rates.
The European Commission's anti-trust authorities had never previously imposed such big fines overall, Competition Commissioner Joaquin Almunia told a press conference.
In total, four financial institutions were involved in a cartel which rigged the Euribor rate and six in a cartel which manipulated the Tibor rate.
In the Euribor case, British bank Barclays benefited from immunity and will not pay a fine because it revealed the existence of the rigging to the commission.
Deutsche Bank was, however, fined 466 million euros, and Societe Generale and RBS were fined 131 million euros in the Euribor case.
The fines on these three banks were reduced by 10 per cent because the companies co-operated with the investigation.
Investigations are continuing concerning French bank Credit Agricole, HSBC of Britain and US bank JPMorgan.
In the Tibor case, Swiss bank UBS avoided a fine because it revealed rate rigging to the commission.
Deutsche Bank was fined 259 million euros, RBS 260 million euros, JPMorgan 80 million euros, US bank Citigroup 70 million euros and British broker RP Martin 247,000 euros in that case.
The investigations and fines come after a separate scandal broke over the rigging of the London Libor rate which is used as a benchmark for many types of financial contracts around the world.
The Euribor, Tibor and Libor interest rates are calculated slightly differently but fulfil a vital function as a reference for the rates which banks are charging to lend each other.
Contracts covering a vast range of financial instruments and vast amounts of money depend in part on the interest rates indicated by Euribor, Tibor, and Libor.
