Melbourne could have more people than Sydney within 30 years, a new population forecast shows.

Victoria is expected to have a population explosion in the next 50 years, as well as a rapidly ageing population.

Australian Bureau of Statistics projections show Melbourne could grow from 3.8 million to 5.3 million by 2026 -- and by 2056 it could swell to almost 8 million, with Sydney then at 7.6 million.

But a leading demographer, Dr Bob Birrell, said it was unlikely Melbourne would outgrow Sydney, and there would be a mass exodus from Melbourne if it became too crowded.

ABS used trends in fertility, life expectancy at birth, net overseas migration and net interstate migration to make the population projections.

Three models were developed to estimate growth.

In one, Melbourne's population would exceed Sydney's by 2039 if migration continued to increase. Other models, assuming lower migration levels, showed Sydney would still be Australia's most populous city.

Meanwhile, Australia's 21 million is projected to increase to 31-42 million by 2056. By 2101 it is expected reach 33-62 million.

http://www.news.com.au/heraldsun/story/0,21985,24295598-2862,00.html