One of the MPs whose vote could consign the Morrison government to a humiliating loss on the floor of Parliament is unsure whether to back a bill to fast-track medical treatment for refugees on Manus Island and Nauru.

Independent Cathy McGowan, who announced on Monday she will not recontest this year's election, told The Sydney Morning Herald and The Age she would not make a final decision on the legislation until it comes to a vote when Parliament resumes in February - giving the Coalition an opportunity to avoid what loomed as the first serious defeat of a government in the House of Representatives in 90 years.

Independent MP Cathy McGowan, who will retire from Parliament at the next election, says she will decide what to do when the bill comes to a vote. Credit:James Wiltshire

Ms McGowan will meet Prime Minister Scott Morrison in Sydney on Tuesday to discuss a range of issues about regional Australia but stressed the medical transfer bill is not listed as a topic for discussion.

The bill to compel ministers to more readily approve medical transfers of refugees from the islands to hospitals in Australia was widely thought to have the support of enough crossbenchers to pass and cause a major embarrassment for Mr Morrison just weeks out from a federal election campaign.