The proposal is part of the party's broader tax policy, released on Wednesday, aimed at creating a fairer system and preventing tax avoidance.

The party believes setting a cap at the average of a company's worldwide debt level would prevent it from artificially inflating debt levels in Australia. It would also help raise $1.75 billion.

Leader Richard Di Natale said the existing tax system is full of loopholes that need to be closed.

"We need to have a tax system, not a tax avoidance system," he told ABC radio.

Senator Di Natale said businesses need to start paying what they owe - the corporate tax rate here - instead of artificially reducing their profits.

He also wants millionaires to pay a minimum rate of tax and to stop reducing their taxable income to zero.

The Greens suggest:

* The ATO reduce its spending on consultancies and instead hire another 4000 staff.

* Making public any settlement the tax office reaches with companies.

* Introducing a Buffett Rule - limiting the amount of deductions those on incomes over $300,000 can make.

* Creating a mining super profits tax of 40 per cent and overhauling the Petroleum Resource Rent Tax.

* Opposing the government's corporate tax cut.

Australian Associated Press