By Michael Holden

LONDON (Reuters) -Prince Harry can take some of his lawsuit against Rupert Murdoch's British newspaper group to trial but allegations of phone-hacking were too late, the High Court in London ruled on Thursday.

Harry, younger son of King Charles and the late Princess Diana, is suing News Group Newspapers (NGN) over multiple alleged unlawful acts he says were carried out on behalf of its tabloids, the Sun and the now-defunct News of the World, from the mid-1990s until 2016.

NGN had argued during hearings in April that the claims should be struck out because they fell outside the six-year time limit for legal action to have been brought.

Harry's lawyers said the prince had not made a claim sooner because there was a "secret agreement" struck between Buckingham Palace and senior figures at NGN to avoid embarrassment.

News Group denies any such agreement, while the palace has not commented.

The NGN case is one of four that Harry, who now lives in California with his wife Meghan and their two children, is pursuing at the High Court against British publishers as part of what he has cast as a mission to hold tabloid executives to account for lying and covering up wrongdoing.

The prince has long spoken out about his anger at press intrusion which he blames for the death of his mother Diana, who was killed when her limousine crashed speeding away from chasing paparazzi in Paris in 1997.

HISTORIC CASE

In June, he became the first senior British royal for more than 130 years to give evidence in court when he appeared as part of his lawsuit against Mirror Group Newspapers.

On Thursday, Judge Timothy Fancourt agreed the phone-hacking allegations were made too late for the Murdoch case, but said the rest of Harry's claims could proceed to a trial which is due to begin in January next year.

"I consider that the Duke’s claim for voicemail interception (and for any other wrongs accessory to any voicemail interception) are time-barred, both in relation to the News of the World and The Sun," Fancourt ruled.

"That is because the Duke has no realistic prospect of establishing at trial that before the applicable date he did not know and could not with reasonable diligence have discovered facts that establish a worthwhile claim in that regard."

In 2012, the newspaper group issued an unreserved apology for widespread hacking carried out by journalists at the News of the World, which Murdoch had been forced to shut down amid a backlash, but it rejects allegations of any wrongdoing by staff at the Sun.

Court documents submitted by Harry's legal team for the April hearings also said his elder brother Prince William, the heir to the throne, had settled a phone-hacking claim against NGN for a "huge sum".

NGN said Thursday's ruling was a "significant victory".

"In arguing his case, the Duke of Sussex had alleged a 'secret agreement' existed between him/Buckingham Palace and NGN which stopped NGN from asserting that the Duke’s claim had been brought too late," an NGN spokesperson said.

"The Judge, Mr Justice Fancourt, found his claims in relation to the alleged 'secret agreement' were not plausible or credible."

(Reporting by Michael Holden;Editing by Bill Berkrot and Andrew Cawthorne)