Prince Harry says he is “deeply concerned” by the Mail newspaper’s “unchecked power, influence and criminality” and is determined to hold its publisher to account.
His testimony was released as part of his privacy lawsuit against Associated Press.
In it, he has also said that he has distanced himself from the royal family’s discussions on taking legal action on phone hacking.
He appeared in the high court for the second day on Tuesday.
Six claimants – including the Duke of Sussex and Sir Elton John and Baroness Doreen Lawrence, mother of murdered teenager Stephen Lawrence – say their personal information was illegally obtained and used as material for the Daily Mail and Sunday News.
Associated Newspapers dismissed the claims as “bad smears” based on a “fishing trip”.
In Duke’s statement, he criticizes the publisher’s efforts in court this week to have the case thrown out on legal grounds.
“The word unfair is inadequate to describe the fact that Associated is trying at this early stage to prevent me from bringing my claim,” the statement said.
“If the most influential and popular newspaper in the UK can avoid justice without an investigation into my claims, what does that say about the industry as a whole and the consequences for our great country.
“I am making this request because I love my country and because I am deeply concerned about the unchecked power, influence and criminality of the Associated Press.”
The report details the stories Duke claims are based on illegally obtained personal information.
They include statements about his relationships with two girlfriends.
He also criticizes a story about his brother William and his reaction to the Italian media publishing pictures of his dying mother.
“It’s really disgusting,” he says, a “vulgar title” and “an obvious reference to a phone call.”
“My brother and I were relatively young at the time (I was 21) and we had private conversations about photos of our dead mother in the public domain.”
In his witness statement, Prince Harry said the royal family – which he referred to as the company – were withholding information from him about the possibility of legal action in response to media intrusions.
He said he started talking to a senior lawyer for the royal family when he started dating his now-wife and “slanderous stories” were published.
Prince eventually learned he could take legal action over phone hacking in 2018, he says.
“The agency made it clear that we knew nothing about phone hacking and it was made clear to me that the royal family was not sitting in the witness box because that would open a can of worms,” he said.
Co-owner Sir Elton John has meanwhile accused a private investigator of tapping his home phone and that of his gardener.
He said it was a “violation of our home and the safety of our children and loved ones”.
Sir Elton is seeking damages over 10 articles, for which he says the email subjects “misappropriated information they stole from our family and friends”.
In his witness statement, he said he used the mail to “find information shared in confidence using love, communication, trust and bonds”.
Sir Elton’s lawsuit against Associated Newspapers claims a private investigator obtained details about his health, including that he “collapsed on the plane”.
Her husband David Furnish has also made the claim in the High Court legal action.
Her statement reveals that actor Liz Hurley told the couple that their live phone calls were intercepted by an investigator working on the email on Sunday.
He said the investigator learned that Sir Elton did not own a mobile phone and used multiple landlines.
Ms Hurley alleged that her calls were also tapped.
Baroness Lawrence claims private investigators working for the Daily Mail tapped her home phone and hacked her voicemails.
In his affidavit to the High Court, he also alleged that the magazine hired investigators to monitor his bank accounts and phone bills.
He says he believes the Daily Mail, which has campaigned strongly for justice for his family, but concludes “I’ve been played for a fool”.
The Associated Press dismissed his accusations as “terrible and completely unsubstantiated calumnies”.
The publisher said the claims were based on the words of private investigator Jonathan Rees, who has served prison terms for perverting the course of justice.
Last year, the Associated Press said in a report: “The cynical and dishonest planners of these claims appear to have persuaded Baroness Lawrence – for whom the Mail has the greatest respect and admiration – to endorse the word of such a man. An outright discredited and untrustworthy liar.”
But Baroness Lawrence, in her witness statement released by the court, said she feared the private investigators’ actions may have undermined investigations into Stephen’s murder.
In his statement, he said, “We developed a good relationship with the press, and by February 1997 we had aligned ourselves with the Daily Mail, and have always presented ourselves as anti-corruption fighters, defenders of truth and justice. Those who really cared about the responsible villains and my son’s killers walking free.”
But when he discovered the alleged use of private investigators, he said there was a “level of trust” and “the betrayal I felt when it was taken away was intense and I realized it was untrue”.
He added: “I can’t think of any less action or behavior than a mother who has murdered and buried her son and stolen information from people pretending to be my friends.
“This is a new shock and injustice to me.”
Allegations in the lawsuit against Associated Newspapers include wiretapping, “hacking” of voicemail messages and the use of private investigators to obtain personal data.
More than 70 journalists have been implicated by allegations made by seven plaintiffs: Prince Harry, Sir Elton John and his husband David Furnish, Sadie Frost, Liz Hurley, Baroness Doreen Lawrence and Sir Simon Hughes.
Their names cannot be disclosed for legal reasons.
The legal arguments on Tuesday centered on ledgers of payments by Associated Newspapers (ANL) to 19 private investigators who allegedly worked for journalists in the past.
The seven claimants say these are large sums of money and evidence that illegal methods were used to collect information about them.
In 2011 the ledgers were revealed to the Leveson inquiry into journalistic standards.
The ANL is trying to remove part of the case because the Leveson files cannot be used in other cases due to confidentiality rules.
The firm also says two barristers in the case and Sir Simon Hughes were closely involved in the Leveson inquiry and gave an “undertaking” not to release documents they obtained.
ANL’s barristers told the court that if the evidence is to be used in the present case, the government should remove these restrictions. This did not happen, they said, so sections of the case relying on the registers should be deleted.
But David Sherborne, representing seven people suing Associated, told judge Mr Justice Nicklin that the ledgers had actually been obtained by an investigative journalist, not from the Leveson inquiry.
As a lead barrister at the Leveson inquiry, representing victims of press intrusion, he personally agreed not to disclose confidential information.
But that promise ended when the inquiry report was released in 2012, he said.
The court also released a witness statement from private investigator Gavin Burroughs, who denied all allegations of hacking phones, tapping landlines or bugging cars on behalf of the Daily Mail on Sunday or the Mail.
Addressing specific allegations by Prince Harry, Baroness Lawrence, Elton John, David Furnish, Sadie Frost and Liz Hurley, he said: “I was not instructed or commissioned by the Sunday Mail or the Daily Mail to carry out illegal information gathering.”
Two other private investigators have also testified in court, admitting their role in providing illegally obtained information to journalists at the Daily Mail and Mail on Sunday.
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