Barnaby Joyce rallies against sex-selection abortions in Sydney

Nine months out from the New South Wales state election campaign, One Nation recruit Barnaby Joyce has appeared in Sydney, declaring politicians are fearful of losing their jobs.

The New England MP was the headline act at a demonstration in front of state parliament on Tuesday evening, which demanded tighter controls on abortion.

"I don't know much about lots, but I know lots about politics," Mr Joyce said.

"And the one thing politicians fear is losing their job.

"What I see before me here is about 1,500 people who can hand out how-to-vote cards."

A private member's bill to ban abortions for the purpose of sex selection is due to be debated in parliament on Wednesday.

The practice was already banned under NSW Health policy and formally opposed by parliament in 2019, when MPs voted to decriminalise abortion.

However, Libertarian MP John Ruddick wants to explicitly outlaw abortions for sex selection reasons, and introduce penalties for medical practitioners who perform them.

Under his bill, they could face fines of up to $22,000 or up to five years in prison.

Mr Joyce, who travelled from Canberra for the event, told the crowd they must "keep the fire burning".

"Yet, for some unknown reason, if they're in utero, it's OK."

Mr Joyce conceded speaking out on the issue could be a turn-off for some voters.

"Politically, does this make you popular? Nup," he said.

"But you know why you do it? Because it's the right thing to do."

NSW Health says sex-selection abortions 'rare'

Supporters of Mr Ruddick's bill pointed to a study last year from Edith Cowan University, which aimed to find indirect evidence of a link between sex-selective abortion practices and higher-than-expected rates of male births in some migrant populations.

The study — which examined birth data from 1994 to 2015 — determined there were "patterns consistent with male biased [sex birth ratio] among certain immigrant groups in Australia, particularly from countries with a strong son preference, such as India and China".

"While this may be indicative of prenatal sex-selection, our study does not establish causality," the study concluded.

NSW Health said a 2020 review found the practice was not widespread.

The review found that between October 2019 and September 2020, 15,973 terminations were reported.

Of those terminations, 13 were reported to have been for the "sole purpose of sex selection".

However, the review found that 10 of those cases were likely to be reporting errors, because the pregnancies were terminated within a nine-week gestation period, during which time there was "no readily available and reliable way of determining gender".

Liberal upper house MP Susan Carter told the rally's crowd she would "like to believe" sex selection abortions were not occurring, "but it's just not true".

"We have to stand against this."

Mr Ruddick said if politicians believed abortions were not occurring for sex selection reasons, there should be "no harm in creating a law to say you can't do it".

MPs will get conscience vote

While the bill is set to be debated in parliament, a vote is not expected in the near future.

Both government and opposition MPs will be allowed a conscience vote, meaning they will not be required to vote along party lines.

Health Minister Ryan Park said he would not support the bill.

"I don't want to see this part of health care back in the criminal code and back in criminal legislation," he said.

"It's not allowed at the moment.

Greens health spokesperson Amanda Cohn said introducing criminal penalties for medical practitioners would scare them off providing abortion services.

"It's already against NSW Health policy for abortions to be provided on the basis of sex selection," Dr Cohn said.

"To that end, NSW Health staff would face disciplinary proceedings in their workplace, which is how you appropriately regulate a health procedure -- without criminal penalties."

She said the Edith Cowan University study was "no basis to rewrite our laws" because the data was collected before abortion was decriminalised in NSW.

"It's not reflective of abortion being provided under the current legal framework," she said.