Malcolm Turnbull and Home Affairs Minister Peter Dutton have talked down the need for an inquiry into population policy after calls by one of their own senators.

Both said it'd recently been looked at, and there was plenty of scope to consider the issue without a formal inquiry.

Prominent Liberal senator Dean Smith wants an inquiry into Australia's population, with new forecasts showing it'll hit 25 million - years ahead of previous predictions.

Western Australian senator Dean Smith wants an inquiry into Australia's population amid new forecasts. Picture: AAP. (AAP)

Malcolm Turnbull has rejected calls for an inquiry into population policy. Picture: AAP (AAP)

Senator Smith said new research shows the figure is likely to be reached in August, 22 years early.

Senator Smith has written to the Prime Minister and Treasurer, asking for a senate inquiry.

He also said moderating our immigration intake could give Australia "time to breathe" to develop a revamped policy.

An inter-generational report by the Howard Government found the 25 million mark would be reached years later.

Senator Smith, the author of Australia's same-sex marriage legislation, said the government needs to get ahead of the population debate. Picture: AAP.

Mr Smith said the new prediction raised questions about service provision, infrastructure planning, and job opportunities.

"I think what we need to do here is take some time to accumulate the evidence," he told the ABC.

Apart from population size, the senator said it was important to consider distribution to ensure the growth isn't concentrated around Sydney and Melbourne.

He believes it's possible to have a "civilised national discussion" about population without claims of racism, and political "dog whistling".

Labor leader Bill Shorten said it was important infrastructure kept with population numbers, but said the government shouldn't blame everything on the one issue.

He also repeated his calls for a clamp down on temporary work visas, saying there were now 1.2 million, up 200,000 under the Liberals.

Mr Shorten said the scheme was reducing local wages and taking jobs from Australians.

The calls come after former Prime Minister Tony Abbott called for immigration numbers to be lowered. Picture: AAP. (Supplied)

Former prime minister Tony Abbott has called for the migrant numbers to be severely cut, and Mr Dutton has indicated reducing numbers could be positive.

Mr Abbott today stepped up his calls for a cut in the intake.

"We don't need to be bringing in a city the size of Canberra every couple of years," he told Sydney's 2GB.

"We've got to bring it down fairly sharply if we are to take downward pressure off wages, the upward pressure off housing prices, and if we're going to unclog our infrastructure.

"Our public transport is full. Our roads are blocked."

He also accused Labor of being "in the grip of ethnic activists" and urged the government to do more to differentiate itself for the Opposition.

Mr Abbott said cutting migration numbers, and support for coal, were two issues that could put distance between Labor and government.

Meanwhile, Treasurer Scott Morrison has a differing view, saying it could cost the budget.

Senator Smith, who authored the legislation for same-sex marriage, said the government should get ahead of the population debate and set up a process for better planning and co-ordination.

Home Affairs Minister Peter Dutton has previously indicated that reducing numbers of migrants could be positive for Australia. Picture: AAP. (AAP)

Mr Dutton said he was happy to consider Dean Smith's proposal but said the government had conducted a wide ranging review into migration settings in the last six months.

He also said the government had lowered migration numbers over the last 12 months.The intake fell 10 percent, to 1, 630,000 last financial year, largely as a result of a clamp down on fraudulent applications.

"At the next election, Bill Shorten is promising to increase migration numbers," he said.

"The coalition is delivering a decrease to those numbers.

"Bill Shorten has dodged questions about what he would do with his migration program. He's got all sorts of pressure with people on his left."

Mr Turnbull said there was “plenty of scope” to look at the issues, and he would talk to Senator Smith.

But, he said, the migration program was right, and works “exclusively for Australia’s national interests”.

“We shouldn’t take one more than we need or want,” Mr Turnbull said.

He said the government was being “absolutely more scrupulous” about who comes here.

“It (the program) is a recruiting exercise,” he said.