A defamation expert from Macquarie University in Australia has warned warring families Down Under to watch what they say after a woman who called her in-law a pedophile during a "family feud" was ordered to pay him $30,000 in damages.

Only four people — including the man's son and daughter — heard the remark, which was made during a child access dispute in July last year.

But District Court Judge Judith Gibson, who ordered the payout, said: "The making of an allegation of pedophilia, in the context of a dispute of access and custody, is like pouring oil onto a fire.

"It caused the plaintiff a great deal of anxiety and concern. The fact that a serious defamation was published to persons who are close to the plaintiff does not make it any the less hurtful."

Macquarie law school defamation expert Roy Baker said Australia probably had the most stringent defamation laws of any English-speaking country.

He had not heard of a case like this in 20 years and said most people would be surprised to learn that something said in anger could land them in court.

"This is one of those salutary warnings," he said. "Watch what you say, only say what you mean and if you say more than you mean, you should immediately correct it and probably apologize."

Those involved cannot be identified for legal reasons but the woman who made the defamatory remark was the maternal grandmother of the child at the center of the dispute.

She admitted she was in a "terrible mood" and "just went off my head" before making the allegation about the child's paternal grandfather.

The court heard that when the man's daughter answered the door, the grandmother told her: "You know your dad's a pedophile - a complete stranger came up to me in the street and told me."

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