Whale Oil blogger Cameron Slater could be facing jail time if he is found to be in contempt of court.
A businessman, Matthew Blomfield, is accusing Mr Slater of breaching a confidential judicial settlement conference in the High Court in Auckland.
Mr Blomfield is also suing Mr Slater in a separate defamation case.
He has accused the blogger of breaching an undertaking that he gave to the court that he would not publish information about Mr Blomfield that was not already in the public domain.
Justice Asher said the contempt allegation was serious. He said Mr Blomfield was seeking a prison sentence if the breach was proven.
Mr Slater, who has been representing himself in court, said the blog post Mr Blomfield was complaining about was actually written by his wife while he was flying back from the Gallipoli commemorations.
He said he apologised to the High Court judge involved in the conference and said he had strong words to say to his wife.
But he also said his wife was frustrated by the court process.
Justice Asher told Mr Blomfield he was surprised that he had not mentioned the apology letter.
He said, normally, if the pair were lawyers, he would ask them to sit down and hammer out what the facts were but he did not believe the pair were capable of that.
The court also heard allegations from Mr Blomfield that Mr Slater had breached an undertaking he had given to the court not to publish further information about him that was not already in the public domain.
But Mr Blomfield said that had happened.
Initially he had 25 breaches but that was whittled down to 12 during today's hearing.
Some of them include comments on the blog site by readers.
Mr Slater pointed out that many of the alleged breaches pre-dated the date of the undertaking. He said others were of a trifle or incidental nature.
Mr Blomfield said one of the breaches was designed to intimidate his witnesses in the defamation case. He said other breaches made disparaging comments about him.
Mr Slater said he now wanted that undertaking to be cancelled because Mr Blomfield had been active in the media and had talked to other blogs.
Justice Asher said that application would need to be heard separately.
The judge has reserved his decision.