Australian opposition leader Sussan Ley, the first woman to head the Liberal Party, is under renewed pressure after the resignation of her shadow defence minister Angus Taylor. His resignation paves the way for an expected leadership challenge. Local media say he has long been plotting to oust her.

Ley narrowly defeated Taylor in a leadership contest last year, after her party's worst-ever election loss. But since then she has been plagued by poor poll numbers and infighting among the conservative Liberal-National coalition.

The coalition, a partnership dating back to the 1940s, has twice split and reunited under her leadership, further undermining her tenure.

Taylor - from the conservative faction of the party as opposed to Ley's moderate wing - on Wednesday announced he had quit the party leadership team, though he would continue to serve the Liberal Party. We have failed to hold a bad Labor government to account, he told reporters, adding that the party needed to protect Australians' way of life and focus on restoring their standard of living.

He stated that he did not believe Ley was in a position to be able to lead the party as it needs to be led from here. It is unclear if Taylor's allies in Ley's shadow cabinet will follow with resignations of their own. According to local media, Taylor's supporters are now expected to request a special party room meeting to consider a so-called spill motion, which would mean the party's leadership is up for contest.

A victory for Taylor would put an end to months of speculation around Ley's leadership, which has never seemed secure. The coalition reunited after its most recent split just days ago, following a row over hate speech laws for which Ley had pushed after the Bondi Beach attack in December, but which her Nationals colleagues refused to support.

Recent polls have shown the populist One Nation party overtaking the Coalition to take second place behind Labor, raising further concerns for Ley's leadership prospects.