Banks would be banned from performing more than one of four basic functions under a Greens plan aimed at preventing Australians being ripped off.
Instead of courting conflicts of interest by being everything to everyone, the party says financial institutions need to revert to specialising in either basic deposits and loans, superannuation, insurance or complex wealth management advice.
Greens leader Richard Di Natale says the current system doesn't work in customer's best interests.
"It's time that banks became banks again," the senator said in a statement.
"Our banks should be working for us, not operating in this toxic culture that encourages and rewards bad results for customers."
How financial institutions are regulated would also change under the policy, with the Australian Competition and Consumer Commission given the job of banking watchdog.
That would mean the ACCC taking over responsibilities now held by the Australian Securities and Investments Commission and Australian Prudential Regulation Authority.
The party believes ASIC in particular is simply not up to the job.
"ASIC is just too close to the banks and is more interested in keeping the financial sector happy than it is in protecting consumers," Senator Di Natale said.
The Greens would also like a Financial Regulator Assessment Board to advise the government each year on how regulators have performed.