Former NSW One Nation leader Mark Latham is on the hook for an estimated half a million dollars in legal costs over a defamatory tweet about Sydney MP Alex Greenwich.

In a decision last year, the Federal Court awarded Greenwich $140,000 in damages over a highly graphic and offensive comment posted on Twitter, now X, in March 2023.

Greenwich’s barrister, Dr Matt Collins, KC, told the court that the tweet, which described sexual activity in graphic and offensive terms that The Sydney Morning Herald has chosen not to publish, was a “vile, homophobic attack” on the openly gay Greenwich.

Federal Court Justice David O’Callaghan on Friday ordered Latham to pay Greenwich’s legal costs of the defamation case on the ordinary basis, which results in the successful party recouping about 70 per cent of their bills. The Sydney MP’s costs have been estimated at more than $600,000.

The parties had engaged in a protracted legal fight over costs following the judgment last year, as Latham resisted paying the bulk of Greenwich’s costs.

Latham’s legal team had submitted he should be ordered to pay only one quarter of Greenwich’s costs on a party-party basis because Greenwich had not succeeded in every part of his case.

O’Callaghan found Latham’s subsequent comments to The Daily Telegraph, which were also part of the lawsuit, did not convey the defamatory meanings Greenwich alleged.

But Collins submitted that “Mr Latham overwhelmingly failed in this case” and he was “not the three-quarters winner”.

O’Callaghan said Collins’ submissions “are irresistible, and they must be accepted”.