Victoria has the lowest birth rate in Australia and is well below the level needed to sustain the state's population without migration.

It is part of a national trend where the fertility rate has declined in Australia since the global financial crisis, with Victoria last year replacing the Australian Capital Territory as the state or territory with the lowest rate, according to Bureau of Statistics data.

In Victoria, the fertility rate is 1.76 babies per woman - well below the replacement rate of 2.1 babies per woman, the level where the population sustains itself.

Professor Graeme Hugo, a demography expert from the University of Adelaide, said Australia-wide the fertility rate had fallen since the economic crisis in 2008 when the national birth rate peaked at just above two babies a woman. He said fertility rates grew strongly from the early 2000s.