Former prime minister Tony Abbott has warned an "extinction" crisis is facing Western nations if more children are not born, while praising the policies of Hungary's far-right leader Viktor Orban.

Key points: Mr Abbott praised Mr Orban for addressing "Hungary's flagging birth rate"

Mr Abbott praised Mr Orban for addressing "Hungary's flagging birth rate" The former Liberal leader suggested Australian politicians should take note of his methods

The former Liberal leader suggested Australian politicians should take note of his methods He also wrote glowingly about new UK Prime Minister Boris Johnson

Writing in the opinion section of the Spectator Australia, Mr Abbott called the controversial politician "the first European leader to cry 'stop' to the peaceful invasion of 2015," in reference to the flood of asylum seekers travelling through Europe at the height of the Syrian conflict.

The former Liberal leader, who lost his seat of Warringah at the May election, said Mr Orban was turning his attention to addressing "Hungary's flagging birth rate" and suggested Australian politicians should take note of his methods.

"The real 'extinction rebellion' we need is not against our failure to reduce emissions more but against our failure to produce more children," Mr Abbott wrote.

"Hungary, whose population is predicted to shrink by a quarter over the next half century, is waiving housing debt for larger families and not taxing at all four-time mothers, among other measures worth careful study."

Mr Orban campaigned on an anti-immigration platform when he was re-elected for a third term in 2018.

Mr Abbott said Australian politicians should take note of Mr Orban's methods. ( Supplied: Hungarian Government )

No fan of the European Union, the Hungarian Prime Minister has also argued against Brussels consolidating its power and undermining the independence the EU's member states.

In the opinion piece, Mr Abbott quoted the man who ousted him as prime minister, Malcolm Turnbull, in defence of his arguments about the declining birth rate.

He quoted Mr Turnbull as saying that the "gravest threat to Western society" was "neither global warming nor international terrorism. Rather it is the unprecedented, sustained decline in the birth rate".

But the quote came from a speech Mr Turnbull, who quit politics after he was rolled as leader last year, made to a population summit more than a decade ago — a vastly different forum to those Mr Abbott has been addressing during his tour of Europe in recent weeks.

Earlier this month he told a Budapest demographic summit called by the Orban Government that a "million angry military-age males" had been "swarming across the borders in Europe".

Brexit battle the modern Falklands fight

Well known as an Anglophile, Mr Abbott also wrote glowingly about new UK Prime Minister Boris Johnson and his efforts to follow through on Brexit.

"In my lifetime, there's never been a more momentous decision, not even that to retake the Falkland Islands," Mr Abbott wrote, referring to Britain's 1982 war to retake its South Atlantic colonies from Argentinian invaders.

"Defeat in the South Atlantic would have been a disaster but would not have left Britain a permanent colony of an EU that despises it."

His pronouncement on the need for Brexit to be a success was joined by a prediction that those advocating to remain tied to the European Union would not follow through on their threats.

"There will be some final huffing and puffing from the re-moaners but leaving the EU won't break up the United Kingdom because the Scots would hardly secede from London only to accede to Brussels," Mr Abbott declared.

Scotland's First Minister Nicola Sturgeon has repeatedly said she will push for another independence referendum if and when Brexit happens, and says an independent Scotland would look to remain a member of the EU.