The head of Australia's largest bank backs a push to save consumers more than $1 billion a year by scrapping credit and debit card surcharges, but thinks the proposal goes too far.

The Reserve Bank is reviewing the nation's payment system and has suggested removing surcharges on eftpos, Mastercard and Visa cards.

It also wants to reduce interchange fees, which businesses pay to card providers.

Speaking at a parliamentary inquiry into the big four banks, Commonwealth Bank chief executive Matt Comyn said he supported the proposal "in essence".

But he urged the RBA not to be too hasty with the changes.

"We think the process is really being compressed," he told the economics committee.

"I think that's led to perhaps some wrong assumptions and conclusions."

Mr Comyn said the plan would m

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