Court hearings began on Monday and law firm Maurice Blackburn, which represents 34,000 ANZ customers, said it would seek to recover fees and protect customers against what it said were "exorbitant" fees and charges.

The case is being heard at the Federal court in Melbourne and could serve as a precedent in cases against other lenders.

An ANZ spokesman said the bank would vigorously defend the law suit and pointed out that this hearing was the first part of a complex case which would likely stretch into 2012.

The claimants are contending that banks in Australia had charged as much as A$1.2 billion a year in unfair "exception" fees while costs for banks were significantly lower.

Exception fees include charges for insufficient funds, overdrawn bank or credit card accounts and late credit card payments, according to the Australian Bankers' Association.

These fees have been discontinued or reduced by most banks over the last two years.

Maurice Blackburn, which filed the suit late, last year, is backed in the ANZ suit by the country's biggest litigation funder, IMF Australia.

Other major banks that could face similar suits include National Australia Bank, Commonwealth Bank of Australia, Westpac Banking Corp, Citigroup, HSBC, Bank of Queensland, Bendigo and Adelaide Bank and Suncorp Metway.