The ACT Council of Social Service and Shelter ACT have challenged Mr Barr's suggestion that the NSW government's purported "chronic underinvestment" in housing for low-income earners has created extra demand for properties in the nation's capital.

Their criticism came after NSW housing minister Melinda Pavey told Mr Barr to "focus on his own backyard and stop playing the political blame game" after learning of his claim.

The ACT government has defended its record on public housing spending, saying its dwelling-to-population ratio was the highest in the country - and more than twice the national average.

However, it was unable to provide hard evidence to support Mr Barr's central claim that a lack of spending on social housing over the border had placed an additional burden on the nation's capital.

ACT Council of Social Service chief executive Emma Campbell said she was "surprised" by the Chief Minister's comment.

"All jurisdictions need additional social housing, and Commonwealth policies like the low rate of JobSeeker also contribute to poverty and homelessness," Dr Campbell said.

"But the major cause of homelessness in the ACT is the chronic shortage of social and affordable housing in the ACT. That is the responsibility of the ACT government.

"We hear so many stories from ACT residents, fellow Canberrans, who are desperate to find decent and affordable housing.

"As Canberrans try to keep a roof over the heads of their children and families they will find little comfort in the political blame game taking place between the chief minister and the NSW housing minister."

Dr Campbell said construction of new public housing dwellings had not maintained pace with Canberra's rapid population growth in the past decade.

Annual report figures show the number of social housing properties in the ACT has actually fallen in the past decade, dropping from 11,848 in 2011-12 to 11,704 in 2019-20. The ACT's population has grown more than 15 per cent in that period.

ACT Shelter chief executive Travis Gilbert was sceptical about Mr Barr's claim.

"If there is evidence significant numbers of NSW residents are relocating to the ACT to find homes on the expectation if they wait it out for six months in a homelessness service to meet residency requirements, [then] they will be allocated one five years earlier than they might get one in Sydney, we'd be keen to meet with the chief minister and have him walk us through that," Mr Gilbert said.

"It would be a big gamble; one punters might regret once they found themselves sleeping in a hatchback on Mount Ainslie in July."

The Canberra Times on Monday morning asked the offices of Mr Barr and ACT housing minister Yvette Berry to provide facts to support the Chief Minister's statement.

An ACT government spokeswoman responded late on Thursday afternoon.

The spokesman could not provide hard evidence on demand from NSW residents on the ACT public housing system, but did offer a prediction based on the overall number of people arriving in the territory each year.

It presumed that five per cent of all interstate arrivals would be eligible for housing assistance, which meant about 900 people a year. People must prove they have lived in the ACT for six months when they apply for support, except for emergency cases.

The spokeswoman said the Barr government was making "significant, nation leading" investments in growing and renewing its public housing stock, pointing out that if all states and territories were matching the territory's commitment then $9.5 billion would be injected into properties across Australia.

The spokeswoman said all jurisdictions faced challenges in building up their housing stock, which is why the ACT continued to lobby the federal government for support.

The ACT has a considerably higher number of social housing properties per capita than NSW, with some 2750 units for every 100,000 people in Canberra compared to about 1800 units per 100,000 in NSW.

Public housing wait times are also far shorter in the ACT than in the surrounding region. Applicants are waiting 3.5 years to be allocated a standard property in the ACT, compared to five to 10 years in Queanbeyan.

There are about 3000 social housing dwellings in the southern NSW district, which extends from the Cooma area up to Goulburn.

While Mr Barr did not respond directly to questions, he did use social media to draw The Canberra Times' attention to a 2019 report highlighting the scale of homelessness in NSW.