The Consumer Law Centre Victoria has published a 90 page report, Unfair Fees:
A report into penalty fees (pdf) charged by Australian banks (the Unfair Fees Report). 

Penalty fees are those fees charged to
customers by banks for customer defaults, for example cheque and direct
debit dishonour fees, account overdrawn fees and credit card late
payment fees.
The
Unfair Fees Report finds that penalty fees charged by Australian banks
could be unlawful under the legal doctrine of penalties if they are out
of all proportion, extravagant and exorbitant in comparison with banks’
costs in processing customer defaults. In addition,
penalty fees are more likely to be levied on low-income consumers, as
they are the least able to avoid the fees.

The Unfair Fees Report makes several recommendations to tackle the problem of penalty fees, including that:

• Australian banks provide information to consumers about their costs in
  processing customer defaults and the income they earn from penalty
  fees;
• Australian banks offer a low-cost Basic Bank Account to low-income consumers that does not levy excessive default fees; and
• The Reserve Bank of Australia undertake a comprehensive study into penalty fees charged by Australian financial institutions.

The Australian Bankers Association has denied the allegations of over-charging.