A signature planning policy designed to boost Canberra's housing supply is unlikely to deliver the nearly 150,000 homes the government expects, a tripartisan committee has warned.
An inquiry into the new territory plan has urged the government to consider further zoning changes on some of the capital's largest blocks to encourage more housing.
The new territory plan, which was unveiled last year, outlined zoning changes to RZ1 blocks including unit-titled occupancies being allowed on blocks above 800 square metres.
But the Legislative Assembly's standing committee on planning has cast doubt on whether this would be enough to meet the territory's population growth.
"The committee is of the view that the dual occupancy may be limited in its uptake," the report said.
"Evidence presented to the committee suggests that the RZ1 changes are likely to have limited impact on meeting the housing targets for the expected population growth."
Liberal member of the committee Mark Parton went further in additional comments, saying the size of the second dwelling should not be limited. Under the change, the second property cannot not be larger than 120 square metres.
He said this should be dropped and the government should include an option to allow separate titling.
"I fear that the change in this space will not result in more than a handful of additional dwellings," Mr Parton said.
"My view is that because of the restriction in the size of the second dwellings... it's not likely to be viable for many homeowners to proceed with a second dwelling."
Greens member and committee chair Jo Clay also called for a city limit to be set for Canberra, marking a significant divergence from Labor's position.
Ms Clay said it was time to set a city limit, saying the size of Canberra was comparable with that of Greater London which has a population of 7 million.
"Everyone needs a home. But we can't sprawl endlessly into our precious habitat. We need to prioritise high-quality density with ample green space to build a truly liveable Canberra," she said.
"Mature cities set city limits. Canberra is already the size of Sydney and Greater London. It's time to stop the sprawl."
Ms Clay also called for RZ2 zoning, which allows for low rise flats, to be applied to RZ1 blocks.
The report's release came on the same day Chief Minister Andrew Barr told an event, held by the Committee for Economic Development Australia, the government had to develop land both in the city centre and in new suburbs.
"We want more people living in our CBD but we will also need new suburbs," he said.
"The approach to meeting new housing supply needs to be multifaceted. It can't just be about infill and it can't just be about new suburbs. It needs to be the totality."
Ms Clay also called on the government to allow Housing ACT, the agency managing the territory's public housing, to buy land at a cheaper rate.
"Housing ACT must pay market rates to buy land to build public housing.
They can't afford to do this because ACT government doesn't fund them enough to do it. ACT government already sells land at cheaper rates to some buyers, but they don't do this for Housing ACT.
"Selling land to Housing ACT at rates they can afford would mean we'd have more public housing in well-serviced areas that support people to have a good quality of life."
Greater Canberra, a housing advocacy group, has been calling for similar changes as part of its "missing middle" campaign and said the report reflects was it had been saying.
"The committee's report validates what the Missing Middle Canberra coalition has been saying all along - the interim territory plan simply doesn't allow the abundant infill housing we need for the future," a spokesman said.
"The strong cross-partisan support for greater density is very encouraging, and the government must deliver this in the final version of the territory plan."
