The $50-million class action suit filed by 34,000 ANZ customers has taken a first step forward by starting on Monday hearings in a Melbourne Federal Court.

The lawsuit was filed last year to protest charges for late credit card payments and overdrawn accounts. Legal proceedings were issued by the court in late 2010.

"This hearing will answer important questions regarding the definitions within the contracts between ANZ and its customers of what is a fee or a charge," class action principal Andrew Watson of Maurice Blackburn law firm was quoted by Herald Sun.

The account holders said they were charged $30 or more for late payments and overdrawn accounts, but they said the amount collected from them was too much.

It will likely be a landmark decision if ANZ was charging excessive fees for overdrafts, which may have implication on similar fees charged by other Australian banks.

"If we're successful in our claims against ANZ, it is likely that other banks will need to front up to the reality that their contracts contain the same problems with charging exorbitant fees," Mr Watson was quoted by ABC.