Prince Harry is not criticising his grandmother, the late Queen Elizabeth, or Britain's royal family over a "secret agreement" with Rupert Murdoch's UK newspaper arm, his lawyer told London's High Court on Wednesday.

Harry, the younger son of King Charles, is suing Murdoch's News Group Newspapers (NGN) for multiple unlawful acts allegedly committed on behalf of its tabloids, the Sun and the now-defunct News of the World, from the mid-1990s until 2016.

NGN, which has settled more than a thousand phone-hacking cases over the past decade, is trying this week to strike out Harry's claim and a similar case brought by British actor Hugh Grant, arguing they should have taken action sooner.

However, Harry says that he did not bring a lawsuit earlier because an agreement was struck between Buckingham Palace and senior figures at NGN to avoid embarrassment.

In a witness statement which was made public on Tuesday, Harry said his attempts to progress the case, with the backing of the queen, were stonewalled by NGN and royal aides.

His lawyer David Sherborne told the court on Wednesday that Harry did not bring his lawsuit previously because of the agreement with NGN, which denies its existence.

Sherborne said Harry was "told more" about phone hacking in 2012, when Harry says in his witness statement that he was told his voicemails had been intercepted, "but that was essentially dealt with by his family ... and their solicitor".

"This is no criticism of the queen or his family," Sherborne said. "That is how it was done and he accepts it. As he explains, he had to."

Sherborne added that Harry was "kept out of the loop" about phone hacking and that he did not believe NGN "would have been stupid enough to go after his messages".

Harry said in his witness statement that royal staff were in communication with Rebekah Brooks - now chief executive of Murdoch's British arm News UK - and News Corp Chief Executive Robert Thomson about his lawsuit.

Sherborne said that, if the case goes to trial, "there will need to be evidence" from Brooks and Thomson about the secret agreement.

Harry has said NGN settled his brother William's phone-hacking claim "for a huge sum of money in 2020... without any of the public being told, and seemingly with some favourable deal in return for him going 'quietly' so to speak".

Buckingham Palace have not commented and William's office said it could not comment on ongoing legal proceedings. NGN has disputed the existence of a "secret agreement" but declined to comment on whether it made a settlement with William.

The case is one of four Harry is currently pursuing against British publishers, following claims in his Netflix documentary and memoir 'Spare' accusing tabloids of widespread unlawful activity and his family of colluding with them.

The preliminary hearing is expected to conclude on Thursday, with a trial due in January if the judge allows it to go ahead.

Harry, who now lives in California with his family, was not in court, but watched proceedings by video link, Sherborne said.

Grant was also watching the proceedings remotely due to "unavoidable filming commitments", Sherborne said, but planned to attend in person on Thursday.