Opposition Leader Bill Shorten has put housing affordability at the heart of his pitch to the party faithful, announcing a multi-billion-dollar plan to subsidise rents for low- and middle-income earners.

Key points: Mr Shorten will open the ALP national conference by countering the Coalition's attacks on his negative gearing policy

Mr Shorten will open the ALP national conference by countering the Coalition's attacks on his negative gearing policy He will announce a scheme which will give investors a subsidy if they keep rent on their properties below market value

He will announce a scheme which will give investors a subsidy if they keep rent on their properties below market value Mr Shorten will present Labor as a united, coherent party

Opening the ALP national conference in Adelaide, Mr Shorten will seek to counter the Coalition's attacks on his negative gearing policy, declaring Labor "the party of home ownership" and "the party of affordable housing".

"A hidden struggle in this country is being fought by the hundreds of thousands of our fellow Australians who can't afford to live anywhere near where they work," he told the conference.

"They're spending over a third of their pay packet on rent — and plenty more on petrol each day when they travel.

"Housing affordability is a national challenge and it demands national leadership."

Under the 10-year, $6.6-billion scheme, investors who build new properties would get a subsidy of $8,500 a year, on the condition they keep the rent at 20 per cent below market rates.

According to Labor, a family in Sydney paying the average weekly rent of $582 would save $92 while a family in Perth would save around $75 a week.

The announcement effectively signals a return to the Rudd-era National Rental Affordability Scheme (NRAS), which was axed in former prime minister Tony Abbott's first budget.

Criticised for its sluggish start and slow take-up rate, the $620 million NRAS saw 37,000 affordable homes built over a decade, well below the intended figure of 50,000 dwellings in four years.

But the scheme still attracted broad support from peak housing bodies, which argued incentives were needed to encourage Australians to invest in affordable, private housing.

Labor estimates its new multi-billion-dollar plan would see an additional 250,000 houses built over the next 10 years for low- and middle-income earners, going some way towards reducing the enormous waiting list.

Mr Shorten used his speech to present the Labor Party as a united and coherent alternative government, just five months out from an election.

"We are determined, we are united, we are ready," he said.

"Ready to serve, ready to lead, ready to govern."

Last night, the left and right factions caucused separately in Adelaide ahead of the three-day conference, with possible battles looming over industrial relations, trade and border protection policies.