JP Morgan, HSBC and Credit Agricole are going to court to avoid more than $500 million of fines that the European Union tried to impose on them last year for rigging a key industry borrowing rate.

The three big banks breached EU competition rules by fixing Euribor, the Euro Interbank Offered Rate at which banks lend money to each other, and exchanged “sensitive information” while bidding for trades, according to the EU in December. Margrethe Vestager (pictured), the EU’s competition commissioner, said at the time that “the aim of the cartel was to distort” Euribor.

JP Morgan was slapped with the heaviest fine of €337.2 million (£286.7 million) for its participation period of five months. The commissioner fined Credit Agricole €114.7 million (£97.5 million) and HSBC €33.6 million (£28.5 million).

Last week, the trio reportedly lodged appeals at the EU General Court.

Bloomberg, quoting HSBC, says that the bank “maintains it was not part of an anti-competitive Euribor cartel and is therefore appealing the European Commission's decision” and says that the commission has promised to “defend its decision in court.”

The banks involved in the cartel allegedly shared sensitive trading information among themselves during chats online and through mobile phone applications and conspired to adjust benchmark rates to suit their trading positions.