Over the past nine years, the government has sold land for 34,900 new dwellings. In the earlier years, from 2007 to 2011, fewer than half the releases were for units, townhouses and apartments.

But since 2011 numbers have crept up and in the past three years, they have peaked, averaging 81 per cent. In 2014-15, 91 per cent of government releases were for medium-density and unit-style housing. In 2015-16, the figure was 71 per cent.

Real Estate Institute of the ACT chief executive Ron Bell said he hoped the government would now return to a more "rational" split between apartments and detached houses.

He had been told the government was moving to a ratio for new suburbs of 80 per cent of land releases for freestanding houses and 20 per cent for units and townhouses, confining the bulk of apartment developments to its "urban renewal" and infill developments. But the government said it had no fixed ratio.

Mr Bell strongly supported an 80:20 split for new suburbs, pointing to Coombs in the Molonglo Valley as an example of what went wrong when too much medium-density housing was released.

"If you go and have a look at the suburb of Coombs it's an absolute disaster, it's ugly and it's going to be a problem later on, I think," he said.

Mr Bell said buyers wanted detached homes, evidenced by the big demand and big prices paid in suburbs like Throsby, where some sections had sold at auction for $600,000 or more.

He urged the Land Development Agency to return to more "over-the-counter" sales, where land was always available and prices were fixed rather than selling at auction and pushing prices high.

"People want to buy detached housing and you can't buy it, and that's why some of our prices have been absolutely ridiculous," he said.

Prices for units and townhouses had plateaued and even gone backwards in older developments, with only new areas such as the Kingston Foreshore being able to hold their price, he said.

A senior executive in the Economic Development directorate, Simon Tennent, said the change in "composition" of land releases was partly a result in delays releasing land in new suburbs because of environmental approvals and smaller releases than expected.

There was also a bigger focus on higher-density housing along transport corridors.

Master Builders Association ACT executive director Kirk Coningham said builders also wanted to see a swing back towards single-residential blocks, sold at affordable process.

"We have a whole lot of really, really good residential house builders who find it very difficult to build in Canberra because of the lack of affordable land supply," he said.

"Housing our people is one of the fundamental things we need to do as a city. Our pricing for land here is astronomical, and it's like a hernia through Canberra's property market where we see it pop across the border to places like Googong and Murrumbateman. So that's where the demand is being met and Canberra as a city misses out because of that."

Mr Coningham said he, too, had been told of plans to increase the supply of single detached housing blocks and he hoped that eventuated.

The Land Development Agency's figures show the government has fallen short of its overall land releases over the past decade by 10 per cent, or 4170 sites. The worst years were from 2011 to 2014, when the government fell 5200 sites short of its 15,300 target.

In the most recent year, 2015-16, the government exceeded its target by 511 sites, selling land for 4024 homes.

Land Development Agency deputy chief executive Ben Ponton said the agency had exceeded its target in six of the past 10 years.

The failure to meet targets from 2011 to 2014 was a result of delays and fewer releases than planned in parts of Gungahlin because of federal environmental approvals, he said.

Underlying demand, which measures forecast population growth and the rate at which new households are formed, was for 15,000 dwellings over the past five years, whereas 17,800 had been released.

The increase in single residential blocks this year and last came after the resolution of environmental issues in Gungahlin and Molonglo, Mr Tennant said.