Prince Harry’s legal action against newspaper publishers over phone-hacking is likely to take a year to come to court, it has emerged, as pressure builds over the tabloids’ treatment of the royal family.

His decision to join group litigation launched by others who have said they were victims of phone-hacking came shortly after his wife, Meghan, the Duchess of Sussex, sued the publisher of the Mail on Sunday for disclosing a handwritten letter she had sent to her estranged father.

In Harry’s lawsuit the publishers of the Mirror, Sun and now defunct News of the World are to face allegations in court that evidence of misconduct has been concealed and destroyed, according to members of Hacked Off, the campaign group that works closely with victims of what it terms “press abuse”.

Such claims are being repeatedly raised in the phone-hacking cases currently before the courts. Senior executives of what was then News International were cleared in 2014 of perverting the course of justice.

News Group Newspapers, publisher of the Sun and the now defunct News of the World, has confirmed that a claim has been issued against it by the prince. Reach Plc, which now owns the Daily Mirror, is also aware that proceedings have been issued.

Hugh Tomlinson QC, chairman of Hacked Off, told the Guardian that the case illustrated the need to re-open the uncompleted Leveson inquiry.

“Prince Harry’s case reminds us of the scale of wrongdoing by certain newspapers which went on over many years,” Tomlinson said. “Hacked Off has long campaigned for part two of the Leveson inquiry to find out what actually happened. This reminds us of the need for that.

“It’s interesting that the action brought by the Duchess of Sussex reminds us that the press misconduct, which newspapers have said is a thing of the past, is still continuing. It emphasises the urgent need for an inquiry.”

Prince Harry’s phone-hacking action was first reported by the Byline Investigates website, which has been monitoring what is known as the mobile telephone voicemail interception litigation (MTVIL) that is being managed by Mr Justice Mann in the chancery division of the high court.

Because there are so many claims against Newsgroup Newspapers and Mirror Group Newspapers the cases have been joined together and are being heard in regular batches. Most are settled out of court through payments; the prince’s claims are not expected to come to trial, if they reach court, until next October at the earliest.

Many familiar faces from the phone-hacking inquiry are likely to face questions again about their past role.

In December 2015, Alison Saunders, then the director of public prosecutions, said that after studying files submitted by police, in relation to corporate liability at News Group Newspapers and against 10 individuals at Mirror Group Newspapers for alleged phone hacking, she had decided to cease pursuing criminal investigations against Rupert Murdoch’s News UK, and against Piers Morgan and other former editors at Mirror Group Newspapers.

The solicitor understood to be representing Prince Harry in the latest phone-hacking claims did not comment.

Responding to the duchess’s legal claim, the Mail on Sunday has defended its publication of a private letter to her father.

The newspaper carried a report quoting Thomas Markle, 75, the duchess’s estranged father, saying he had not intended to share a private letter sent by her but felt pressured to do so after he was “mischaracterised” in a magazine article.

The retired lighting director said he was “devastated” when it was first mentioned publicly in the American magazine. He said: “I decided to release parts of the letter because of the article from Meghan’s friends … I have to defend myself. I only released parts of the letter because other parts were so painful. The letter didn’t seem loving to me. I found it hurtful.”

• This article was amended on 7 October 2019 to clarify that the claim is against News Group Newspapers, publisher of the Sun and the now defunct News of the World.