The Greens want a new national body to protect the rights of renters and improve the standard of rental properties after a survey on the party's website revealed "thousands of horror stories".

The party said nearly half of the 3190 tenants who responded to its survey reported that they were paying 50 per cent of their income on rent.

More than two-thirds said they paid at least 30 per cent – the level considered "rental stress". Nearly 1000 tenants said they felt unsafe in their rented home.

The third force in Australian politics wants Canberra to takeover responsibility for rental standards from the states by introducing a national tenancy act.

The national body would enforce minimum standards for properties, make it harder to evict tenants with little notice, usher in the option of leases longer than 12 months, and investigate ways to make rent "more stable and fair" by considering restrictions on increases.

The Greens would help landlords get their properties up to scratch by offering $500 per property for upgrades to meet the new standard, at a cost to the budget of $1 billion over 10 years.

It comes as experts call for an overhaul of renters' rights – including long-term leases and a standard right to do minor alterations – to reflect that following the housing a growing percentage of the population will rent for life.

Greens housing spokesman Scott Ludlam said: "We have national standards that cover our health and education system, work safety – even plastic chairs have a standard. Our housing system should be no different."

Fairfax Media this month reported that the percentage of the population in private rental properties increased from 18 to 26 per cent over the past 20 years.

The Greens said the Parliamentary Budget Office estimated the policy would cost $474 million over the next four years. They said it would be paid for by restricting negative gearing to existing investments and reducing exemptions to capital gains tax.

Story by Adam Morton

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