Demand for public housing dwellings is set to hit 12,950 households by 2020, based on the now-expired 2012 public housing asset management strategy, up about 17.7 per cent since 2010.

But that five-year strategy, which guides how Housing ACT runs its 10,902 public housing dwellings, expired in January last year, and only in August this year did Cabinet agree to develop a new one, as it was a requirement of signing up to the new national housing agreement.

While the government is replacing about 1288 dwellings, in order to sell off land to help fund the light rail project, it faces continued criticism for not growing the total pool of dwellings, given rising demand.

The demand forecast in the 2012-15 strategy estimated a need for 11,000 dwellings in 2010, rising to 12,030 by 2015 and again to 12,950 in 2020.

There were 1778 households on the waiting list as at the end of September, and only 10,902 dwellings available.

The government would need to build a further 2048 public housing dwellings in the next 14 months, if it was to meet the demand expected by 2020.

When the Canberra Times asked Housing ACT about the current level of demand earlier this year, a spokeswoman said the forecast had not changed, but the government was considering potential improvements to the methodology.

But the government has not responded to the question as to why the strategy was not updated sooner, nor why there was no reconsideration of the real level of demand in the intervening six and a half years.

Public housing advocates have previously cited concerns the level of demand may be much greater than estimated, but people were not bothering to apply, given wait times of more than 1000 days for most applicants.

The spokeswoman did say in a statement the government was developing a long-term strategic plan for the asset management of public housing in the ACT, but there was no response to interview requests with senior Housing ACT staff to help explain the matter.

Asked last week why the government took 18 months to make a decision to develop a new strategy, a spokeswoman for Housing Minister Yvette Berry said in a statement "while the strategy officially drew to a close in January 2017, we have continued the work of the strategy through the delivery of the public housing renewal program".

"At the same time, there has been a coordinated effort across government to identify new and emerging issues facing public housing," she said.

Ms Berry's spokeswoman also said the government acknowledged a number of dynamic factors influenced demand for public housing, and the new five-year plan would "respond to a range of emerging drivers and trends affecting the demand for public housing, including the type and volume of stock that will be required to meet contemporary tenant need".

But the statement also said the new plan would not be completed until after the renewal program ended next July, indicating the government might be preparing to release its new affordable housing strategy without updated demand forecasts.

ACT Council of Social Service director Susan Helyar said the government had to ensure the demand forecast was completed before the strategy was announced, because the government would not know what the current or future demand would be without it.

She said if the forecast was not completed until July, it would be several more years before the stock was in place to meet current demand, let alone future growth in population.

"Every year people have to wait for new stock to be available is another year they can't get ahead financially because they're spending such a high proportion on housing, they can't afford to save a deposit to buy a house, and they're often compromising on health, education and expenses," she said.

"[We] paint a bleak picture because our members have told us it has been urgent since 2016 for the government to deal with the lack of affordable housing in this city.

"We really need the new strategy to set some ambitious targets and allocate the level of resources needed to deal with the scale of the problem this city faces."