After the Australian Securities Investments Commission released its review of remuneration in the $1.3 trillion mortgage market, consumer group Choice and mortgage brokers have asked for a probe regarding referral fees that allegedly do not serve the interests of consumers.

Banks pay a type of spotter's fee to people who are likely to come into contact with home buyers and send these customers to the bank. However, critics argue that there is a lack of transparency in this area as banks would not specify the exact size of these commissions.

"Referral fees are murky. Right now we don't know who pays what to who as part of the mortgage referral process," said Erin Turner, Choice head of campaigns. "After all, referral fees are designed to increase business for bankers, not to get consumers a better or fairer deal on a mortgage."

These fees, which amount to thousands of dollars, are usually received by trusted advisers like lawyers, accountants, and real estate agents. While banks claim that these commissions are always disclosed to customers, only ANZ specified the size of its referral fees, which are "predominantly" 0.3 per cent of the loan amount. Other major banks reveal a range from 0.2 to 0.5 per cent of a loan, which is up to $2,500 for a $500,000 mortgage.

"From a consumer perspective, consumers should know if someone is being paid to refer them to an individual lender. And the question then comes down to what is the basis of the referral?" said John Flavell, chief executive of Mortgage Choice. "Is it about the consumer's best interest or is it about the best interest of the individual that's referring?"