The Duke of Sussex has been barred from alleging that the Princess of Wales and her family were victims of unlawful information gathering as part of his own privacy claim against the publisher of the Daily Mail newspaper.

Prince Harry’s lawyers told the High Court earlier that the duke’s “associates” including the Prince and Princess of Wales had been targeted by private investigators paid by journalists.

The duke, 41, later complained that he had not been aware that William and Kate, both 43, would be identified in his High Court case. The Prince of Wales has avoided becoming embroiled in litigation with newspapers over alleged unlawful information gathering.

Harry’s lawyers said that private investigators were paid for information about Prince William’s 21st birthday party, a mobile telephone conversation about Kate and details of her family’s homes.

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Mr Justice Nicklin ruled on Friday that the allegation relating to Kate had been added to Harry’s claim too late. The allegation about William’s party was never formally part of the claim but the judge struck out allegations that three private investigators were paid for information about William.

The judge said he was rejecting irrelevant allegations to stop the case “descending into an uncontrolled and wide-ranging investigation akin to a public inquiry”.

The duke is suing Associated Newspapers, publishers of the Daily Mail and the Mail on Sunday, as part of a group of celebrities including Sir Elton John, Sadie Frost and Liz Hurley. The group claim to be victims of unlawful information gathering including blagging and hacking.

Harry and the Princess of Wales

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Nicklin has barred claims that journalists commissioned “burglaries to order” as part of his privacy claim. Harry’s lawyers made the allegation that two financial journalists burgled the home of the businessman Michael Ward in 1992 to steal documents as they prepared an article about an investigation by the Serious Fraud Office.

Nicklin ruled that the single alleged burglary identified, along with many other claims made by the celebrities, could not be considered.

“Even if proved true, they cannot assist in the fair resolution of the claimants’ claims,” the judge ruled on Friday about the burglary allegation. “It is not alleged that this incident has any connection with any claimant, or any pleaded journalist.”

In his 16-page ruling, the judge said that resolving these allegations had become “extremely complex” and an “involved side-show”.

He criticised Harry’s lawyers for maintaining the burglary claim, saying: “[It] reflects a continued and fundamental misunderstanding of the proper scope of this litigation … It also reveals an unreasonable approach to the costs implications of litigating in this way.”

Associated Newspapers denies any wrongdoing and has described allegations as “lurid” and “simply preposterous”. The duke’s lawyers are considering an appeal against the judgment, which may delay the start of the nine-week trial set to begin in January.

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The judge ruled that the celebrities could not claim that evidence of an alleged “propensity” of one journalist to use unlawful information gathering proved that another journalist was also involved.

The judge criticised Harry’s barrister, David Sherborne, for attempting to rely on evidence in the duke’s case against the publishers of the Daily Mirror and The Sun.

Nicklin said that in a ruling in July, “I explained why I did not derive much assistance from general comparison between this litigation and previous cases”.

He noted: “Undeterred, Mr Sherborne has, at this hearing, referred me to several decisions from these earlier cases. I have read the decisions carefully. I am not persuaded that these decisions assist me in resolving the proper limits of evidence of propensity.”

The judge ruled that he would not consider whether unlawful information gathering had been allegedly “widely and habitually carried out” at the Association Newspapers title.

“Quite simply, establishing whether [unlawful information gathering] was widespread and/or habitual at Associated is the territory of a public inquiry,” he said. “It is not necessary to determine that issue for the fair resolution of the claimants’ claims.”