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 Taylorin 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 said 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.

When announcing the initial split in January, Nationals leader David Littleproud pointedly said his party could not serve in a shadow cabinet under Ley.

A series of recent polls have shown the populist One Nation party - which only got 6% of the national vote last year - overtaking the Coalition to take second place behind Labor. Ley's personal ratings are also poor.

The coalition has failed to agree on what caused its crushing election defeat to Labor, which saw the Liberals all but wiped out in the major cities.

Immediately after the election the coalition briefly split amid argument over climate and energy policy including its commitment to a net-zero emissions by 2050 policy, which the Liberals later agreed to abandon under pressure from the Nationals and its own right-wing.

The Nationals are based in rural areas and lean more conservative than the Liberals. Political analysts say the recent surge in One Nation support has pushed them further to the right in a bid to win back votes at a time when the Liberals need to appeal to more centrist voters in the cities.