Two senators at the centre of a bitter, personal feud are reaching out to their supporters for help covering their legal costs in an anticipated defamation case.

Greens Senator Sarah Hanson-Young is threatening to sue her libertarian rival David Leyonhjelm after he told her to “stop shagging men” on the floor of the Senate and made further comments about her personal relationships in subsequent TV interviews.

READ MORE Legal showdown looms between Hanson-Young and Leyonhjelm

Senator Hanson-Young’s campaign has already raised $25,000 in donations after two days, while Senator Leyonhjelm has secured nearly $10,000 in three days.

Lawyers representing the Greens senator have already filed a concerns notice accusing Senator Leyonhjelm of damaging their client’s reputation by implying she was a “slut” who “shags men indiscriminately” and “hates men”.

The letter gave Senator Leyonhjelm seven days to apologise and pay damages, or a court proceeding would be launched.

But Senator Leyonhjelm has refused to apologise, despite the prime minister and others from across the political spectrum urging him to do so.

“I’m not backing down,” Senator Leyonhjelm told his Facebook followers.

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“I've been inundated with offers to help. So we're building a war chest. If you want to be a part of this fight to stop the toxic ideology of the Greens then please give what you can.”

Senator Leyonhjelm is the Liberal Democrats’ only elected member and has made a name for himself as a ‘free speech’ campaigner.

He says his comments were justified because he was “offended” by the Greens senator implying “all men” were rapists. Senator Hanson-Young strongly denies this claim and there is no recording of her making the comment.

Senator Leyonhjelm’s donations will go to fighting the defamation case as their “first use” while the remainder will be donated to the party for future election campaigning, according to the GoFundMe site.

If Senator Hanson-Young wins her case and is awarded costs and damages, all the money donated will be divided between two charities: Plan International and the Working Women’s Centre SA.

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If she loses, her legal costs will be drawn down from the pool of donations.

The Greens campaign was set up and supported by prominent media personality and feminist Jane Caro and academic Simon Chapman.

“I’m taking this action on principle, for all women who have had enough,” Senator Hanson-Young said.

“For women everywhere, from the factory floor, to the hospitality industry, to flight attendants, this fight is for you.”