The program would involve government constructing and then holding multi-unit developments to boost the supply of longer-term rentals in a high-demand housing market.

It came as new figures by Corelogic on Wednesday showed national rents had been driven up by 10.2 per cent, due to a lack of vacancies.

Labor's housing spokeswoman Rose Jackson said affordable rentals were not on the market because of a dwindling supply, as NSW continues to grow.

The pilot, which would be completed in the first two years of a Labor government, gave regional voters "a clear choice" in the March elections.

"More of the same extreme rent rises and almost no affordable rental stock under the Liberals and Nationals - or a NSW Labor government that takes this challenge seriously and is prepared to get directly involved to solve it," she said.

Under Labor's plan the government's land and property development arm, Landcom, would find surplus government land, work with local government on potential sites and look for opportunities to acquire land to build on.

Any properties built on surplus government land will be subjected to Labor's mandate for 30 per cent of dwellings being kept for social housing.

Another government agency would manage the homes and collect rents - reinvesting profits into social housing.

But Treasurer Matt Kean slammed Labor's proposal as "very modest" and pointed to the coalition government's pipeline of 12 built-to-rent schemes, including 500 units in central Sydney.

NSW's social housing waiting list increased in 2022 for the first time in six years, reaching more than 51,000.

Developers welcomed the bipartisan push on build-to-rent, calling for an additional 300,000 well-located new homes to be built within six years.

"Build-to-rent (BTR) is a growing sector in Australia, providing increased security of tenure alongside high amenity," Urban Development Institute of Australia said.

"However it has been slow in NSW with currently only 1,200 BTR apartments under construction.

"It is critical that whichever party is elected in March delivers upon these commitments to increase the supply of new housing to help alleviate the affordability crisis in NSW."

The Greens want to scrap land-tax concessions given to big developers for build-to-rent schemes where they don't deliver affordable housing.

Greens housing spokesperson Jenny Leong said an immediate rent freeze was necessary to slow down the market.

"It costs more to rent now than ever before because of years of special treatment to big developers, landlords and investors," she said on Wednesday.

"We need an immediate rent freeze now to stop out-of-control rent rises and give renters urgent relief while longer-term rental reform is implemented".

Australian Associated Press