Within hours of Prime Minister Malcolm Turnbull leaving for the United States, his predecessor was openly criticising government policy and casting doubt on re-election.

Key points: Tony Abbott proposed cutting Australia's migration intake by 80,000 places

Tony Abbott proposed cutting Australia's migration intake by 80,000 places He issued a blunt rebuke to Scott Morrison after the Treasurer hosed down his proposal

He issued a blunt rebuke to Scott Morrison after the Treasurer hosed down his proposal He said Mr Morrison was guilty of "swallowing" advice from "so-called experts"

The former prime minister's proposal to drastically cut Australia's migration intake by 80,000 places was publicly shut down by Cabinet ministers Peter Dutton and Scott Morrison on Wednesday, who said it would be a $4-5 billion hit to the budget.

Mr Morrison, a former immigration minister in the Abbott cabinet, said the former prime minister did not discuss this proposal with him while he was prime minister and did not understand what he was trying to achieve.

But Mr Abbott issued a blunt rebuke to Mr Morrison on Wednesday afternoon, saying his criticism was simply "wrong".

He said Mr Morrison had been "captured by his department" and was guilty of "swallowing" advice from "so-called experts".

Mr Abbott also singled out Mr Turnbull — who will not land in the US until later today — for his decision to cite 30 Newspoll losses as one reason for replacing him as leader.

"I want us to win the next election," Mr Abbott told Sydney radio station 2GB.

"Sure, people like Scott can say everything we are doing is right … but if you believe the polls — and it was the Prime Minister, let's face it, who sets such great store by the polls — obviously we aren't doing everything right.

"If we want to have a fighting chance of winning the election, some things have got to change."

Mr Abbott used his regular Wednesday afternoon interview on the station to defend his immigration plan as "principled, pragmatic and maybe even popular".

On Thursday morning, Mr Morrison said more Australians would be struggling with the cost of living if the economy had not been boosted by migration in recent years.

"He's wrong." Mr Abbott said.

"It's all very well sitting down with public servants and so-called experts and swallowing their advice, but if it's such good advice, why is the Government perceived so poorly?

"If you are fair dinkum about winning the next election, and I have some experience of winning elections and winning seats off the Labor Party, you can't just live in this Canberra bubble."

Sorry, this video has expired Peter Dutton speaks at the National Press Club on immigration

Mr Dutton hosed down Mr Abbott's immigration proposal at the National Press Club, saying the Government had its policy settings right.

Mr Morrison said permanent migration to Australia had remained relatively stable since 2011, and that a perceived increase was due to a jump in international students and overseas tourism.

He said last year, the amount of permanent migrants coming to Australia did not meet the cap for the first time in many years.

These arguments did not have much credence with Mr Abbott, who warned his colleagues they may cost them the election.

"Frankly, it's about time the insiders showed a bit more respect to those who feel like outsiders," Mr Abbott said.