Prince Harry was dealt a setback in his long-running legal campaign against Britain’s tabloids on Tuesday after a high court rejected a bid to draw Rupert Murdoch into allegations about how Mr. Murdoch’s London papers dug up personal details about him and later concealed or destroyed evidence of it.

Justice Timothy Fancourt ruled that lawyers for Harry and about 40 other plaintiffs could not amend their complaint against News Group Newspapers, publisher of The Sun, to include Mr. Murdoch, the 93-year-old media mogul who controls the company, as well as other senior News Group executives.

“There is a desire on the part of those running the litigation on the claimants’ side to shoot at ‘trophy’ targets, whether those are political issues or high-profile individuals,” Justice Fancourt declared in the 284-page ruling. “This cannot become an end in itself. It only matters to the court so far as it is material and proportionate to the resolution of the individual causes of action.”

“The trial,” he added, “is not an inquiry.”

The judge also rejected Harry’s attempt to broaden the time frame of the alleged unlawful actions to before 1996 and after 2011, saying his lawyers had filed that amendment too late. That rules out allegations of actions targeted at his late mother, Diana, Princess of Wales, or his wife, Meghan.

The case, which is scheduled to go to trial in January, will mark one of the final chapters of the sprawling litigation that flowed out of the phone-hacking scandal — an episode that upended Britain’s newspaper industry, triggered the closing of a major tabloid, News of the World, and led to changes in journalistic practices.

Harry has been at the vanguard of that effort, filing lawsuits against three London publishers for what he says was a decades-long campaign of unlawful intrusion. The litigation has produced some notable victories, including a judgment last December against the publisher of the Daily Mirror that it had hacked his cellphone and used other unlawful methods to gather information on him.

But Harry has also had setbacks. In July 2023, Justice Fancourt threw out his claim against News Group that it had hacked his phone between 1996 and 2011, on the grounds that his lawyers had waited too long to file it. The judge allowed Harry’s claims of other unlawful acts, including the hiring of private investigators, to go ahead. On Tuesday, the judge noted that Harry had not yet removed claims of hacking from his complaint and would have to do so before the trial began.

News Group said in a statement that the court had “thoroughly vindicated NGN’s position.” The company’s lawyer, Anthony Hudson, had argued that the plaintiffs were trying to sweep in Mr. Murdoch and other well-known figures to make the case “a vehicle for wider campaigning against the tabloid press.”

Testifying before Parliament in 2011, Mr. Murdoch said he should not be held personally responsible for the hacking, given that he ran a global company with 53,000 employees. But he shut down News of the World, the tabloid most closely linked to hacking, and issued a contrite apology. In recent years, Mr. Murdoch has been more preoccupied by lawsuits stemming from Fox News’s coverage of the aftermath of the 2020 presidential election in the United States.

In explaining why he wouldn’t accept Harry’s amendments, the judge noted that the trial was already set to air allegations of a coverup by “trusted lieutenants” of Mr. Murdoch, including his son James; Rebekah Brooks, the chief executive of News U.K.; and Will Lewis, a former News executive who is now the publisher of the Washington Post.

The judge did allow lawyers for the plaintiffs to add Mr. Lewis’s name to a list of executives who they allege were part of a plan to conceal evidence of hacking by removing files from a computer belonging to Ms. Brooks. The files were transferred to a USB drive that either was lost or has not been opened because it was encrypted, according to the amended complaint.

News Group noted that Ms. Brooks was questioned about deleting emails during her criminal trial in 2014, and was cleared of the charges. Mr. Lewis, who helped manage the response to the hacking scandal, was never charged. He went on to be chief executive of Dow Jones & Company, publisher of The Wall Street Journal, before being named publisher of The Post last November.

A spokeswoman for Mr. Lewis declined to comment. In 2020, he told the BBC that allegations of wrongdoing were “completely untrue.”

For Harry, who now lives in Montecito, Calif. and only occasionally visits Britain, the lawsuits have often seemed as much about casting a harsh spotlight on the tabloid press and its major players, as about winning the cases.

Last June, he testified against Mirror Group Newspapers, becoming the first senior member of the British royal family to take the stand in court since 1891, when Queen Victoria’s eldest son, Prince Albert Edward, testified in a case about wrongdoing during a game of baccarat at which he was present.

In emotional testimony, Harry said the stream of negative stories about him and family members had led him to distrust even his closest friends. Many stories had focused on Harry’s relationship with a former girlfriend, Chelsy Davy, who he said had found a tracking device on her car.

In February, two months after his victory over Mirror Group, he reached a settlement worth at least 400,000 pounds ($508,000) on the remainder of his privacy claims. The prince singled out the former editor of the Daily Mirror, Piers Morgan, whom he said, “knew perfectly well what was going on.” Mr. Morgan, who is now a broadcaster, has denied being involved in hacking.

Harry also claimed that his brother, Prince William, had been paid a “huge sum of money” by News Group to settle claims that it hacked his cellphone. The settlement, he said, was part of a “secret agreement,” in which the family would defer legal claims against the company and thus avoid the spectacle of having to testify about embarrassing details from their intercepted voice mail messages.

Neither News Group nor Kensington Palace, where William has his office, have confirmed such an arrangement.

Judge Fancourt said he understood the motives of lawyers in wanting to pull Mr. Murdoch and other big names into the case. He likened it to investigative journalists finding missing pieces of a jigsaw puzzle and suggested that the lawyers were playing as much to the press as to the court.

“This is in a sense understandable, as the psychology of investigative journalists or those who love jigsaw puzzles,” he wrote. “But the question for the court is a different one: what is needed for a fair trial of the individual claims to take place?”