The federal Greens are calling for a new "millionaire's tax" and want taxes to rise, not fall, in next week's federal budget.

Key points: Greens want to add 5 pc tax on every dollar over $1 million

Greens want to add 5 pc tax on every dollar over $1 million Change could create $680 million over four years

Change could create $680 million over four years Greens say extra revenue could be spent on infrastructure, including renewable energy

Greens say extra revenue could be spent on infrastructure, including renewable energy Push to raise Australia's tax take to 26 pc of GDP

The party wants an extra 5 per cent tax slugged on every dollar over $1 million in personal annual income, saying it would reap $680 million over four years.

"To make society more equal, we need more tax, starting at the top," Greens treasury spokesman Adam Bandt said.

"We would rather have an Australia where everyone gets great public education and healthcare, which means being upfront about growing our revenue base by getting rid of unfair tax breaks and asking the very wealthy to pay more."

The Greens want Australia's tax take to rise to 26 per cent of Gross Domestic Product (GDP), up from about 22 per cent

The minor party, which could find itself with the balance of power if the election goes down to the wire, has outlined its budget principles ahead of next Tuesday.

It said Government should take advantage of low interest rates to borrow for infrastructure, including transport and renewable energy.

And it argued debt should be allowed to grow to 25 per cent of GDP.

"It's time to stop treating debt like a four-letter word," Mr Bandt said.

"There's no point in having a AAA credit rating if you don't use it.

"It's better to have a small deficit and well-funded public schools than a small surplus and an undereducated society."

The Greens said the Government should borrow up to an extra $75 billion over the next decade to fund productive infrastructure, saying it could happen while net interest payments stayed below 2 per cent of GDP.