Veteran newsreader Peter Mitchell has apologised to a Supreme Court judge for an on-air blunder made last week, while reporting on the upcoming murder trial for Peter Dupas.

The Channel 7 presenter was slammed by Justice Lex Lasry for language used during the 25 second report, which breached instructions handed down to media in the courtroom on March 14.

Justice Lasry said the report was an extremely serious breach of contempt laws, ordering Mitchell and Channel 7 executives, including news director Simon Pristel, to the Supreme Court to explain their actions.

"The action is not in contempt of the court, but it almost is. The very thing we talked about not happening is exactly what occurred," he said.

"Mr Dupas is entitled to a fair trial. I made the mistake of assuming the media understood that.

Channel 7's barrister William Houghton QC explained to the court that there was “breakdown in the process prior to broadcast by Mr Mitchell” who went “off-script” and “added words”.

"He recognises your honour that he shouldn’t have used those words. That was regrettable and unfortunate and we have apologised for that," Mr Houghton said.

A visibly frustrated Justice Lasry accepted the apology but said it was "bleedingly obvious" details broadcast should not have been.

"This is thumbing one's nose at the court, isn't it? This is not an entertainment issue," he said.

The television network requested the case not be referred to the Director of Public Prosecutions.

"We offer a sincere and genuine apology," Mr Houghton said.

"Our journalist was in court and passed on the warning but it did not reach Mr Mitchell."

Dupas' defence barrister John Desmond said what had occurred was "highly reckless in the extreme".

"It is Dupas who keeps suffering."

He requested his client's identity be suppressed in the future to ensure a fair trial, to which Justice Lasry said he had "not much choice but to do that".

Prosecutor Andrew Tinney said it was "pleasing to see the response from Channel 7 and comforting to know it was not deliberate".

But he said it was “extremely worrying that a newsreader and senior person would go off script like this.”

"There must be processes in place to ensure this does not occur again."

Justice Lex Lasry will review the matter and the footage and parties will be advised when a decision is made.

© Nine Digital Pty Ltd 2018