Federal MP Anne Webster, her husband, and the not-for-profit organisation they founded to support young mothers, have been awarded a total of $875,000 in defamation payouts over a series of "vile" and "unjustifiable" online posts made to Facebook earlier this year.

Dr Webster, the Nationals member for the regional Victorian seat of Mallee, sued online conspiracy theorist Karen Brewer in the Federal Court over a series of posts and videos published on the social media site across a two-week period in April and May.

In her judgement, Justice Jacqueline Gleeson found the posts claiming that the Websters and Zoe Support were "participants in a secretive criminal network involved in child sexual abuse" were false and untrue.

She said the defamatory publications "spread along the grapevine into the Mildura community" — where Dr Webster's husband, Phillip, is a GP — via her Facebook page and its several thousand followers.

While the judge found reasonable people would dismiss Ms Brewer's rants as "deranged and lacking in credibility", she accepted that "suggestible members of the Mildura community may have considered them credible".

Justice Gleeson, who said the Websters had "suffered intensely", awarded Dr Webster aggravated damages of $350,000, her husband damages of $225,000 and Zoe Support damages of $300,000.

Taking a stand

Speaking after Tuesday's judgment was handed down, Dr Webster said she was interested in exploring legislative changes that could lead to publishers, such as Facebook, being made more accountable for material published online.

"It’s not an unknown world — but it is a bit of a scary world — where people can share whatever they like and it’s only by going through legal cases that things can change," she said.

"I wasn’t so aware of the whole conspiracy theory at the time — for me, it was an issue of justice and it was to make a stand."

Dr Webster, a former social worker with a PhD in sociology, said she hoped that people who used social media to falsely attack others would realise that their actions were not only harmful but could have costly ramifications.

Claims 'wholly indefensible'

Ms Brewer, who the court previously heard was based in New Zealand, did not file any defence to the defamation claim, made no attempt to justify her posts in court, and had not retracted her statements.

"It should have been obvious to Ms Brewer, at all relevant times and if she were capable of rational consideration on the subject, that her defamatory statements were wholly indefensible," Justice Gleeson said.

She said Ms Brewer's conduct — including posting another video targeting the Websters in late August — justified awarding aggravated damages against her.

"This evidence tends to confirm that Ms Brewer is obsessive and defiant, and may not be deterred by this proceeding from further defamatory publications concerning the applicants," Justice Gleeson said.

Deterrent to young mothers 'most harmful'

The court heard some of the posts were shared hundreds of times, including by one Mildura business, and that monthly referrals to Zoe Support had dropped since one of the posts in late April.

Zoe Support helps more than 150 mothers aged from 13 to 25 and their children to access education and medical appointments each week, and Justice Gleeson said any effect the untrue posts had in deterring young women from seeking support was "perhaps the most harmful aspect" of Ms Brewer's offences.

Several witnesses, including Mildura state MP Ali Cupper, former federal Liberal MP Chris Crewther and Mildura Mayor Simon Clemence, gave evidence attesting to the Websters' integrity.