Nauru is a “very pleasant island” where refugees and asylum seekers get better healthcare than in some towns in regional Australia, Tony Abbott has said.

The former prime minister made the comments to 2GB on Monday in an interview warning voters not to toss out Liberal MPs in favour of independents who, he said, claimed to be centrists but were in fact “to the left of Labor” and more like the Greens.

Abbott was asked about a YouGov Galaxy poll, published on Sunday, which found 80% of people want children and their families transferred off Nauru by taking New Zealand up on its offer to resettle 150 refugees.

Abbott said “the people on Nauru and Manus [Island] now are almost all would-be economic migrants and if we give them what they want we will get more of them”.

“Of course kids off Nauru is a good slogan but it’s a dreadful guide to policy because if we aren’t allowed to have kids on Nauru, just bring some kids with you and you automatically get to Australia.”

At the time of a Senate estimates hearing last Monday there were 652 people held on Nauru, of which 541 had been found to be refugees. Another 88 people’s claims were still being processed, and 23 had been rejected.

As of April this year Nauru’s refugee determination process found 89% of people had legitimate claims and were granted refugee status, while another 10% were still waiting.

There is no such thing as an economic refugee under domestic or international law.

In September the Australian Medical Association wrote to the government warning of an escalation in reports of catastrophic mental and physical health conditions among refugees and asylum seekers, especially children.

But Abbott said refugees and asylum seekers “are being very well looked after on Nauru”.

“Health services on Nauru for boat people are much more extensive than the health services that a lot of regional towns get here in Australia,” he said. “Nauru is no hellhole by any means, I’ve been there. If you like living in the tropics, it’s a very, very pleasant island.”

Health organisations, including Médecins Sans Frontiéres, have reported widespread and increasing mental illness particularly among children. MSF said at least 78 patients of theirs had attempted self-harm or suicide, and another 100 people were on their waitlist before Nauru kicked them off the island.

Dr Parbodh Gogna, the recently appointed chief medical officer for ABF, last week told Senate estimates there was a “ramp up” in the number of people presenting to hospital, with a spike around the time of the five-year anniversary which did not abate. Gogna said Nauru didn’t have the tertiary paediatric facilities required to monitor a child with their family to see how unwell they were.

This won’t surprise anyone but Abbott is lying with impunity here. Medical support on Nauru is woefully inadequate and the majority of people exiled to Manus and Nauru by Australia have been found to be genuine refugees. https://t.co/sNxM4B1ljp — Nick McKim (@NickMcKim) October 29, 2018

The government is under pressure from the opposition, crossbench MPs, a former home affairs department official and the Liberal MP Julia Banks to remove refugees and asylum seekers from Nauru.

On Tuesday, Labor offered conditional bipartisan support to pass a bill to prevent refugees settled in New Zealand ever migrating to Australia, but the prime minister, Scott Morrison, repudiated the offer, declaring “you don’t horse-trade on border protection”.

The independent Kerryn Phelps elevated the issue before the Wentworth byelection, and criticised the Liberals for a lack of climate policy.

Abbott was asked about the prospect of an independent running on a similar platform against him in Warringah with Labor assistance, after the author and commentator Jane Caro confirmed she was considering a run and some constituents formed an independent campaign group, Voices for Warringah.

“Well, who knows,” Abbott replied. “I’ve never taken my seat lightly, I’ve always put in a big effort. That won’t change.

“Last time round I had a pretty strong campaign against me and I expect that will be the case again.”

Abbott said that he would encourage the construction of the Northern Beaches tunnel whereas an independent would “sabotage it”. He said he also stood for a strong economy.

“The trouble with these independents is that they claim to be centrists but invariably they’re to the left of the Labor party.

“If you actually look at the views of someone like Kerryn Phelps, on most things she’s to the left of Labor – more like a Green, really.”

At the 2016 election, Abbott faced a campaign from the TV presenter James Mathison, who won 11.4% of the primary vote. Abbott suffered a 9% primary vote swing against him and was elected on 61.5% of the two-party preferred vote against the Greens.

According to polling leaked to the Australian Financial Review, Abbott was on track to lose the seat to Labor 57% to 43% just 10 days out from the election, before the Liberal party redirected resources to retain the seat and Malcolm Turnbull recorded a robocall calling for voters to re-elect the man he replaced as prime minister.