Women and men will make up equal numbers in the Australian Senate for the first time with the anticipated arrival of a former Liberal MP.

Key points: Ms Henderson defeated former Indi MP Sophie Mirabella's husband Greg Mirabella for the Senate spot

Ms Henderson defeated former Indi MP Sophie Mirabella's husband Greg Mirabella for the Senate spot Her arrival will increase the proportion of the government's female Senators to almost 43pc

Her arrival will increase the proportion of the government's female Senators to almost 43pc But despite the Senate milestone, women are still under-represented in Coalition ranks

Sarah Henderson was pre-selected for the Senate spot vacated by former minister Mitch Fifield, after losing the Victorian seat of Corangamite at the May election.

Her return to Parliament will see the number of male and female Senators split evenly at 38 each.

"Upon Sarah taking office the Senate will reach a milestone: equal numbers of women and men for the first time ever," Senate President Scott Ryan said on Twitter.

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Ms Henderson, who defeated former Indi MP Sophie Mirabella's husband Greg Mirabella for the Senate spot, said it was significant.

"Achieving equal numbers of men and women in the Australian Senate is a certainly a major milestone," she said.

"I am honoured that my appointment as a Liberal Senator for Victoria will also make history in this way."

This year's federal election did little to boost the number of women in Parliament overall and despite the Senate milestone, women are still under-represented in Coalition ranks.

Ms Henderson's arrival will increase the proportion of the government's female Senators to almost 43 per cent while female Labor Senators outnumber their male colleagues at more than 61 per cent of the party's Upper House representatives.

"You cannot be what you don't see, which makes it all the more important that young girls see more women in Parliament and in varying roles across the community," Labor's leader in the Senate Penny Wong said.

"Striving towards a society where — regardless of race, sexuality, religion, ethnicity or gender — all people are judged on their abilities alone is a principle held dear by the Labor Party."