Finance Minister Mathias Cormann has again ruled out a royal commission into the banks.

Questioned by Commonwealth Bank whistleblower Jeff Morris, Senator Cormann said there had been a series of inquiries into the financial system.

The government's judgment was that more inquiries without action was not the best way forward.

"We have taken action, we have given additional resources to ASIC (Australian Securities and INvestments Commission). We have responded to the recommendations that have been made by various inquiries," he told the ABC's Q&A program.

Mr Morris said the government's so-called tough cop ASIC was a timid and hesitant regulator and there had been numerous financial scandals on its watch.

"Yet at the same time, your government also takes millions of dollars in political donations," he said.

Labor has called for a banks royal commission, with deputy opposition deputy Tanya Plibersek saying this was a systemic problem which needed a thorough systemic evaluation.

"Every time we hear there's a scandal, the banks say that we're all over it and we have fixed it and it won't happen again. And then there's the next scandal," she said.