Opposition Leader Peter Dutton may not have to pay any of the legal costs of a successful litigant due to possible “sham” bills, his barrister has told three judges.

Refugee advocate Shane Bazzi was ordered in December to pay Mr Dutton $35,000 in damages and some of his legal costs over a now-deleted tweet.

A judge earlier found a six-word tweet labelling the then home affairs minister “a rape apologist” was defamatory.

But in May three Federal Court appeal judges allowed Mr Bazzi’s appeal, set aside the December order and dismissed the proceeding.

The case came back before the judges on Friday to deal with a dispute over costs.

Mr Dutton’s barrister Guy Reynolds SC successfully argued for an adjournment after an affidavit from Mr Bazzi’s solicitor was provided on Thursday night.

His barrister Barry Dean said this was because an error had been discovered in relation to Mr Bazzi’s legal bills.

The court was told of a $233,000 bill sent last December, which was used to assess costs, as well as one sent last October for $155,510.

Mr Reynolds said the latter figure was the exact amount of crowd-funding Mr Bazzi had raised for the trial.

He said he needed to cross-examine the solicitor about the costs agreement between Mr Bazzi and his lawyers.

“It may well be the case that the bills that had been provided at assessment are sham bills, with the possibility that other bills are also shams,” he said.

He also raised the possibility that the actual fees agreement between Mr Bazzi and his solicitors were shams.

Mr Reynolds spoke of the prospect that Mr Bazzi was never liable for anything and the arrangement was that whatever came in from crowd- funding would be what the solicitors received.

“It may be that Mr Bazzi also needs to give evidence,” he said.

He raised the possibility that Mr Dutton did “not have to pay anything at all by way of costs”.

The judges said Mr Reynolds was entitled to some explanation about the billing arrangements. The case was adjourned until November.

– AAP