Harry, 39, the younger son of King Charles, and more than 40 others are suing News Group Newspapers (NGN) over accusations of unlawful activities by journalists and private investigators, for the Sun and the now-defunct News of the World from the mid-1990s to the mid-2010s.
A trial focusing on some of those claims, possibly including Harry's, is due to begin at the High Court in London in January next year.
NGN, which is contesting the claims, has paid out hundreds of millions of pounds to victims of phone-hacking by News of the World and settled more than 1300 lawsuits but has always rejected allegations of any wrongdoing by staff at the Sun.
Prince Harry and others are suing News Group Newspapers over accusations of unlawful activities. (AP PHOTO)
Ahead of the trial, NGN's legal team has sought an order to force Harry to disclose any relevant information that he might possess, or that might be held by his former lawyers or the royal household, which would be relevant to what he knew about alleged unlawful behaviour before the end of 2013.
If Harry knew he had a potential claim against NGN before that date, then the case could be dismissed on the grounds it was filed too late.
Anthony Hudson, NGN's lawyer, told the court that they had no choice but to seek the order, accusing Harry of "obfuscation" and adding the claimant was creating an "obstacle course" on the issue.
Hudson said he was concerned that Harry's team had stated that correspondence between Harry and JR Moehringer, the ghostwriter of his hugely successful memoir Spare, over messaging app Signal had all been wiped.
Hudson added there was no excuse for not searching text or WhatsApp messages between them.
The lawyer said the disclosure of other possibly relevant emails had also been highly unsatisfactory.
"We have had to drag those out of the claimant kicking and screaming," he said.
Harry's lawyer David Sherborne responded by accusing Hudson of using language to "get a headline," and said NGN's legal team were guilty of simply carrying out a fishing expedition.
He said the suggestion Harry was withholding or destroying material was the "height of hypocrisy," saying NGN had deliberately deleted millions of emails as part of a way to hide incriminating evidence.
There was no suggestion that the searches demanded would produce any relevant information, Sherborne told the court, saying a search of Harry's "SJPKP" email account for possible relevant terms had thrown up almost 30,000 hits, of which only a handful might possibly be relevant.
That process had taken 130 hours and cost 50,000 pounds ($A95,000) he said.
Judge Timothy Fancourt said he would give his judgment on NGN's application later on Thursday.
