Australian lenders including Westpac Banking (WBC), Citibank and Australia & New Zealand Banking Group (ANZ) face a class action lawsuit in the country filed by consumers over late credit card fees.

The law firm Maurice Blackburn, which is representing hundreds of thousands of Australian bank consumers, filed the case against ANZ, Citibank and Westpac in the NSW Supreme Court. The suit will include all customers of these banks who have ever paid a late credit card fee.

The wider action follows a case of late 2013, which involved approximately 38,000 ANZ clients in the Federal Court in Melbourne. The Melbourne court ruled in favor of the ANZ customers saying that the penalties were extravagant and unconscionable as they did not reflect the real cost to the bank.The bank has appealed against the decision.

The lawsuit alleges that the banks charged extravagant fees, could be worth millions of dollars and include hundreds of thousands of bank customers.

Maurice Blackburn’s class action practice head Andrew Watson said: "We’re talking about an enormous action."

More than 185,000 Australians have signed up online to be part of earlier lawsuits, as per the data available on Maurice Blackburn’s website cited in Bloomberg.

The law firm is also considering filing further cases against Commonwealth Bank of Australia, CBA subsidiary Bankwest, National Australia Bank and American Express.