The first female leader of Australia's Liberal Party, Sussan Ley, has been ousted after just nine months in the job, losing a leadership ballot to her former shadow defence minister Angus Taylor.

Ley was elevated to the role after the party suffered a resounding defeat in last year's election, but since then has been plagued by poor poll numbers and infighting among the conservative Liberal-National Coalition.

Taylor had announced he would challenge her for leadership of the opposition on Wednesday, ending months of speculation.

In a social media post he said his election on Friday was "an immense honour" and that he looked forward to working with new deputy leader Jane Hume.

Taylor, from the party's conservative faction, won the secret ballot, 34 votes to 17.