Census data from 1996 recorded 307,917 residents in the territory.

There were 288,195 people recorded in ACT in 1991, and 395,790 residents in 2016.

The report, prepared by the office of ACT Commissioner for the Environment Dr Joe Baker, warned that the territory's flora and fauna will be under threat unless the government sets an upper limit on the population or moves to minimise human impacts.

The report said the ACT's population had passed 300,000 and as it increased the number of people per household was declining, exacerbating the problem.

"There are more people and each of those people is taking up more space than previously," the report said.

"There is no denying that increasing human population is currently the biggest direct and indirect threat to the ACT's plants and animals."

Policies would be needed to ensure the population did not rise above that level and to prevent urban sprawl "threatens ACT habitats" more plant and animal habitats being overtaken by suburbs.

Higher density living should be encouraged, the report said.

A spokesman for Environment Minister Gary Humphries said a population limit would be "a very controversial proposal".

"You'd basically have to say no new houses will be built," he said.

"Also, if you were to say no more new development on the edges of the city, then there'd be more and more pressures for urban renewal in the inner city which again would be very controversial."

See: https://trove.nla.gov.au/newspaper/article/130573062