New South Wales MPs from across the political divide have united in a bid to decriminalise abortion, an offence based on legislation dating back to 1900.

Key points: The Crimes Act 1900 includes abortion as an offence punishable by 10 years in prison

The Crimes Act 1900 includes abortion as an offence punishable by 10 years in prison The new bill is based on legislation introduced in Queensland last year

The new bill is based on legislation introduced in Queensland last year Independent MP for Sydney Alex Greenwich said the laws would ensure safe and legal abortions

Independent MP Alex Greenwich will introduce the Reproductive Health Care Reform Bill 2019 to Parliament this week with widespread backing, including that of Health Minister Brad Hazzard and the Australian Medical Association.

Mr Greenwich said he expected a "robust debate" over the bill but was optimistic about the extent of the cross-party support.

"NSW is the only state to not have decriminalised abortion," he said.

"Our bill ensures that women will have access to safe and legal abortions and ensures that doctors have the legal clarity that they have long sought.

"There will be members that will have strongly held personal and potentially religious views, but I hope that all members can put women in NSW first."

The existing laws, introduced under the Crimes Act 1900, make it an offence to "unlawfully administer" drugs or use instruments "with intent in any such case to procure her miscarriage", punishable by 10 years in prison.

In practice, doctors can administer the procedure if "the operation was necessary to preserve the woman involved from serious danger to her life or physical or mental health which the continuance of pregnancy could entail", based on a 1971 court ruling.

The new bill will include the provision for access to an abortion in the first 22 weeks of a pregnancy and is based on Queensland laws introduced last year that stemmed from law reform commission reviews.

The bill will also include a conscientious objection clause for doctors, who would be obliged to refer patients to other medical practitioners.

'Strong support'

Mr Greenwich said there had been extensive support for the bill.

Independent MP Alex Greenwich aims to modernise NSW abortion laws. ( AAP/Joel Carrett )

"There is obviously strong support across the Parliament," he said.

"We've got great supporters within the Labor Party. The Greens have long supported this issue.

"We also have strong support within the National Party, the Liberal Party and on the crossbench, so it's my hope we will get this through."

The working group of MPs behind the bill include Labor's Penny Sharpe and Jo Haylen, and the Nationals' Trevor Khan.

Ms Sharpe, the Shadow Minister for Family and Community Services, said it had cross-party support.

"We're very hopeful that a bill we'll be bringing to Parliament this week has the best chance to get abortion out of the crimes act of NSW," she said.

At present, a medical abortion can be performed up to nine weeks from the woman's last period. A surgical abortion can be carried out within the first 20 weeks of pregnancy.

Ms Haylen said the bill was the culmination of hard work to drive the modernisation of the laws.

"This represents an important step forward for women, who have for far too long had their reproductive health treated as a crime," she said.

The Australian Medical Association NSW said the bill would remove the "stigma and legal uncertainty" around abortion because of its association with the Crimes Act.

The NSW Greens spokesperson for women's rights, Jenny Leong, also welcomed the move.

"It's past time for women to have the right to make decisions about their own bodies," she said.

Dr Rachel Carling from Right to Life Australia said she opposed the bill and slammed Mr Hazzard who backed decriminalisation.

"I find it really disappointing a Liberal Health Minister will be putting his name to such a bill as this — this is not about healthcare for women, this is a social issue from the left," she said.

Dr Carling said she was against "pushing abortion as the first option".

Mr Greenwich acknowledged the work of Greens Senator Mehreen Faruqi, who attempted to bring a bill in 2017 and said this version, in following the Queensland legislation, had a clear legal framework.

Wendy McCarthy, chair of the NSW Pro-Choice Alliance — a collective of more than 70 organisations that launched a fresh campaign for reform in May — said it had been a "very long journey".

Under the proposed reforms, the rights of women and doctors would now be clearly protected, she said.

"I can't think of any other health matter that's been sitting in statute for 119 years which penalises a particular group of people and hasn't been revised — all this will go," she said.

"This is a chance for a new level of respect and decency between women, their doctors and the community, and removing some of the stigma for women who need, for whatever sets of complex reasons, a termination of pregnancy."