A second female cabinet minister has said she will vote against a controversial bill seeking to recognise a 20-week-old foetus as a living person, as the issue divides the NSW government and reignites the abortion debate.

Environment Minister Robyn Parker and Nationals whip John Williams have told Fairfax they will vote against Zoe's Law 2, which is expected to be debated in the NSW Parliament this Thursday.

Supporting Zoe's Law: Attorney-General Greg Smith. Credit:Anthony Johnson

The Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZCOG) has strongly condemned the private member's bill, introduced by Liberal Chris Spence. Pregnant women who ignore their doctor's advice on birth choices, or older mothers who face life-threatening pre-eclampsia, could face serious consequences as a result of the proposed legal change, the obstetrician group has warned.

Health Minister Jillian Skinner came out against the bill last week, after the Australian Medical Association and the NSW Bar Association wrote to MPs raising concerns about its implications, particularly for women wanting abortions.