Australia’s population could hit 30 million by 2029, according to new a projection by the Australian Bureau of Statistics (ABS), with Melbourne also tipped to overtake Sydney as the nation’s largest city around 2050.

The ABS released three projections on Thursday morning, finding that Australia was expected have an extra 5 million people in about the same time, “if not a little a shorter, than the 14 years it took to grow from 20 million to 25 million”. Under the lowest projection, Australia would reach 30 million by 2033.

The medium-growth projection would have Australia hit 42 million people by 2066, compared to 49 million - with fewer assumed deaths, higher life expectancy and migration - or 37 million under the most conservative prediction.

The debate about Australia’s population – which currently stands at 25.1 million – has intensified after the prime minister, Scott Morrison, signalled the government would lower the migration intake in response to concerns “roads are clogged, the buses and trains are full”.

Under all three ABS projections, New South Wales would remain as the largest state with a population of between 9 million and 9.3 million in 2027.

The ABS projected that growth would be fastest in Victoria, where population has been a major campaigning issue at the state election. The state would hit 7-8 million by 2027.

In 2050, Melbourne would be expected to reach 8.5 million while Sydney’s population would have hit 8.3 million under the medium-growth model.

The ABS’s highest projection suggests there would be 12.2 million Melburnians by 2066, compared with 11.7 million people in Sydney. By that point, Melbourne would make up 84% of Victoria’s population.

The projection to 2027 was for Sydney to reach between 6 million and 6.4 million, up from 5.1 million in June 2017. Melbourne’s population would soar to between 5.9 million and 6.2 million, increasing from 4.8 million.

Anthony Grubb, the director of demography at the ABS, said the data suggested Australia could “add a further 10 million to our current 25 million by the year 2043”.



“However, under our higher range of fertility, mortality and migration assumptions, the population would reach 35 million five years earlier in 2038,” he said.

“Conversely, under lower assumptions the population would only reach 35 million a decade later in 2053.”

The ABS said Queensland’s population would increase to 6 million in 2027, Western Australia would reach 3 million, and growth would be slowest in South Australia, where the population would stand at 2 million.

The number of people living in Tasmania is projected to rise to 573,000 by 2027, up from 545,000, meaning the Australian Capital Territory is expected to eventually surpass the island state. The ACT will hit 510,000 in 2027, an increase of about 31,000 people.

The ABS also said the number of Australians aged over 85 would double by 2042.

Liz Allen, a demographer at the Australian National University, told Guardian Australia the projections indicated the population would “not continue to grow as it has done in recent years”.

Allen said the data showed “immigration will continue to be a major contributor to growth but will likely decline in quantum terms”.

“The most likely scenario of population change reflected in the projections released today points to fewer net overseas migrants settling in Australia each year,” she said.

“The projections show that even if net immigration was cut to zero, Australia’s population would continue to grow in the medium term,” Allen added.

The medium-growth projections assumed an average life expectancy of 83 for men and 86 for women and a fertility rate of 1.8 babies per women, with net overseas migration at 225,000.

While the current migration intake cap stands at 190,000 places a year, the government only took in 160,000 people in the last financial year.