Tony Abbott has accused his critics of "carping" on about asylum seekers following his speech on the subject in London last month.

The former prime minister used his Margaret Thatcher Lecture last month to call on European leaders to consider closing their borders to asylum seekers, saying it would "prevent a tide of humanity surging through Europe and quite possibly changing it forever".

But his suggestion that the European Union adopt Australia's policy of turning back boats sparked criticism from within the European community.

In an opinion piece for The Spectator, Mr Abbott defended his remarks.

"In any morality contest, preventing hundreds of deaths at sea surely justifies robust measures to prevent people smuggling," Mr Abbott said.

"This, I said, would 'require some force; it will require massive logistics and expense; it will gnaw at our consciences — yet it is the only way to prevent a tide of humanity surging through Europe and quite possibly changing it forever'."

Mr Abbott said he was pleased his calls had been taken up by some commentators in Europe, despite what he claimed was "carping from the usual suspects".

His comments were welcomed by the leader of the UK Independence Party (UKIP) Nigel Farage, who described Mr Abbott's speech as "heroic".

But Opposition Leader Bill Shorten has described Mr Abbott's comments as "unhelpful".

Turnbull told to tread carefully on tax reform

Mr Abbott also outlined the challenges he said Malcolm Turnbull would face if he wanted to increase the Goods and Services Tax (GST).

He told The Spectator even "politically ascendant conservatives" had to tread carefully when undertaking ambitious reform.

"As a potential reformer, Malcolm Turnbull has the advantage of being relatively unbound by previous commitments, but still faces the problem of how to deal with the 'no-one can be worse off' mindset that makes serious reform so hard," he said.

"Changing the tax burden from income to spending makes sense but only if overall taxes become lower, simpler and fairer."

The Turnbull Government has said "nothing is off the table" as it considers a number of options to either broaden or increase the GST, as well as other tax changes.

Mr Abbott has compared the challenge to that being faced by British prime minister David Cameron, who Mr Turnbull will meet as part of his trip to Europe this weekend.

"The real challenge, in Australia as in Britain, is how responsibly to spend less on short-term consumption and more on long-term investment in infrastructure and national security," Mr Abbott said.

Abbott: adoption laws need to change

In a separate opinion piece published in The Australian, Mr Abbott called for more changes to make domestic adoption easier, saying "politically correct" policies were putting children at risk.

He said there was too much of an emphasis on keeping children with their biological parents, even if those parents had "massive problems".

"Leaving children to parents with a proven record of neglect is the triumph of ideology over common sense," Mr Abbott said.

"Worse, it's the victory of politically correct fashion over decency and compassion."

He has proposed changes which would see fewer children in foster care, and more being adopted domestically.