Victorian treasury coffers would be boosted by $1.5 billion if the state backed a bold Greens policy to slug the big banks with a state-based levy, according to the new parliamentary budget office.

Under the Greens' plan, Victoria would impose a separate 0.015 per cent quarterly bank levy on the state's share of bank liabilities that are already subject to the commonwealth's bank levy.

The proposal is a copy of the former South Australian Labor government's state-based bank levy.

Former premier Jay Weatherill ultimately dumped his proposed bank levy because it was blocked by the Coalition and other parties in the South Australian parliament, but the Greens want to take the policy to the Victorian election on November 24.

The state-based levy would be based on a formula using Victoria's share of the national economy and calculated as the average of Victoria's annual real gross state product as a proportion of Australia's real gross domestic product over the two previous years.

Last year, the Turnbull Government introduced the major bank levy which is currently estimated to raise around $7.4 billion between 2018–19 and 2021–22.

That rate was set at 0.015 per cent and applied quarterly to banks with total liabilities in excess of $100 billion.

Victorian Premier Daniel Andrews told ABC Radio Melbourne he did not support the plan.

Banks can afford it: Greens

Greens Treasury spokeswoman Ellen Sandell said the banking royal commission was showing the banks had racked up super profits with government support.

She also said the state could not rely on the "over-inflated" property market long term.

Ellen Sandell said the big banks should pay more tax. ( Australian Greens Victoria )

"The Greens' plan for a levy on the big four banks, plus Macquarie Bank, will return some of the super-profits of the banks to all Victorians. This means more public money for our schools, hospitals, public transport, and essential services across Victoria,'' Ms Sandell said.

"The big five banks made over $33 billion in profit last year, and their CEOs took home $50 million for themselves. These banks can afford to pay a fairer share of tax."

But the banks have lashed the proposal, saying the idea was "reckless and dangerous".

Anna Bligh, chief executive of the Australian Banking Association said a Victorian bank tax would discourage investment, put a handbrake on growth and hurt jobs.

"This proposal will hurt business confidence, affect investment and make the state a riskier place to do business," she said.

"With about 42,000 people employed by banks in Victoria, the industry is in the top 25 employers in the state."

The Victorian Parliamentary Budget office was recently set up and came into action in June. It is an independent office that costs political promises.

There are less than 100 days before the November 24 election.

Published and private polling indicates that the result will be close, with the Greens in a strong position to potentially hold the balance of power and the party tipped to win more inner-city seats.