The study of heritage guidelines and design controls by Sydney architecture firm Ancher Mortlock Woolley was received by the government in 2012 but never made public.

Released under freedom of information by the Community Services Directorate this week, it calls for conservation, reuse and revitalisation of the Dickson Towers, Owen Flats, pair houses, three-storey flats and maisonettes, designed by architect Sydney Ancher for the former National Capital Development Commission.

The report said degraded and unkempt post-war international modernist-style homes could transition from public housing to private ownership, and new medium-rise buildings be added to the precinct's boundaries.

Unused space could be used for new housing towers to raise funds for new public housing elsewhere in Canberra. The plan would protect the area's role as a "gateway" to Canberra.

The conservation proposals are at odds with government plans to demolish all but two of the buildings so that 1100 apartments can be built in the area.

Chief Minister Andrew Barr plans to raise $400 million from selling the Northbourne Avenue land, along with other government buildings, and the funds will be used for the city to Gungahlin tram line.

Mr Barr said last month just two of the historic buildings should be retained, one on each side of Northbourne Avenue.

The government is facing opposition from the National Trust, which has launched an appeal in the ACT Civil and Administrative Tribunal calling for the precinct to be protected.

The trust's legal standing on the matter is being challenged and a decision is due in May. The ACT Heritage Council gave protection to about 40 per cent of the buildings in February.

The 2012 report calls for the upgrading of homes to contemporary living standards and dwelling sizes by combining small dwellings into larger ones, adding new buildings and improving outdoor spaces.

One of the four-storey bedsit flat buildings on each side of the road's northern end would be retained, along with most of the two-storey pair houses on the western side and all four of the three-storey flats at the southern end of the precinct. All five of the three-storey maisonette buildings on the eastern side and the most northern and southern groups of garden flats should also be kept.

The report calls for underground parking for the redeveloped precinct.

"The total demolition of identified dwellings shall not be permitted except in exceptional circumstances," the report said.

These would include where houses were structurally unsound and beyond reasonable repair or where health and safety risks could not be fixed.

The report calls for original rendering and roof styles to be maintained; for monochromatic tones including buff colours to be used and existing door and window frames to be restored in timber and painted white. Some examples of original interiors would be preserved and the precinct's history would be documented for future study.

The Ancher Mortlock Woolley report is understood to have formed part of a multidisciplinary conservation study of the area completed in 2012 for the government.

No other documents were released.

Mr Barr said ACT government directorates regularly commissioned reports and research to help inform decision making as part of good governance.

"The government sought a number of views and opinions in relation to the redevelopment of the Northbourne housing precinct," he said.

"The decision to sell surplus public housing as part of the asset recycling scheme reflects the government's urban renewal agenda and a desire to achieve the best value of money for the ACT taxpayer and allows us to build new modern housing for our tenants."

The sale of the Northbourne precinct will attract $60 million in bonus payments from the federal government to be spent on the light rail project.

The Property Council and other business organisations have backed the government's plans for the area.