The Australian Greens have accused the Commonwealth Bank of making excessive profits at the expense of their customers.

The CBA on Wednesday announced a record net profit in the six months to end December 2012 of $3.7 billon.

Deputy Greens leader Adam Bandt said the CBA and other big banks were gouging customers with unjustified fees and interest rates out of sync with real costs.

"There is a strong case for the big four to be paying for the de-facto 'too big to fail' policy that underpins their profitability and lowers their funding costs," he said in a statement.

The Greens want to scrap ATM fees for the big four banks - CBA, ANZ Bank, National Australia Bank and Westpac - and require banks to provide "tracker mortgages" that match the real cost of funding.