The state government's tough-on-crime policies are swelling the prison population so quickly it is too late to avoid crowding by building or reopening prisons, the Bureau of Crime Statistics has warned.

Prisoner numbers hit a peak of 10,937 in March, almost 900 more prisoners than a year earlier, or the equivalent of one Parklea prison, internal government data shows.

"Shutting prisons and getting rid of 600 jobs leads to overcrowding.": Paul Lynch. Credit:Jon Reid

A report delivered to former attorney-general Greg Smith by BOCSAR director Don Weatherburn has concluded that the sharp rise in prisoners is not caused by an increase in crime.