Daniel Hanks was paid 250 dollars (£180) to undertake “legitimate” research on Meghan in 2016, the year she first started dating the Duke of Sussex News Group Newspapers (NGN) said.
The publisher issued a statement after the investigator, also known as Danno Hanks, said he had unlawfully accessed detailed information, including the duchess’s social security number.
Mr Hanks made the claim to the BBC with the broadcaster saying it had seen a report compiled by the investigator which was passed to the Sun and featured Meghan’s phone number, addresses, social security number and information on members of her family.
Information on her ex-husband and a former boyfriend were also included, the BBC said.
According to the broadcaster, licensed private investigators in the US can access databases of personal information for certain permitted reasons such as court reports, but it is unlawful to access this additional level of detail for the purposes of journalism.
Mr Hanks told the BBC: “Pretty much everything I found out they could find out themselves using legal means – with the exception of the social security numbers.
“When you have that information … it’s the key to the kingdom.”
NGN said that “at no time” did the Sun request the duchess’s social security number, nor had it used information provided by Mr Hanks “for any unlawful practice”.
Mr Hanks, now retired, who worked as a private investigator for more than 40 years gathering information on celebrities, has been jailed four times, including in 2017 for extortion, the BBC said.
He told the broadcaster the Sun had contacted him following the Leveson Inquiry into press standards and asked him to sign documents, which the BBC said it had seen, that committed him to act lawfully – an assurance he repeated when billing the newspaper for his work.
But Mr Hanks claimed he was not asked where his information was obtained, telling the BBC: “They didn’t care. They just wanted the information.”
The investigator came forward and shared his documents after being contacted and paid by Graham Johnson, a freelance journalist and editor of Byline Investigates, the BBC said.
Mr Hanks said he had done so to “clear my conscience”, adding he was “deeply sorry for what I did”.
In its statement NGN said: “In 2016, The Sun made a legitimate request of Mr Hanks to research contact details and addresses for Meghan Markle and possible relatives using legal databases which he had a license to use. He was paid 250 dollars.
“Mr Hanks was not tasked to do anything illegal or breach any privacy laws – indeed he was instructed clearly in writing to act lawfully and he signed a legal undertaking that he would do so.
“The information he provided could not and did not raise any concerns that he had used illegal practices to obtain the information.
“At no time did The Sun request the social security number of Meghan Markle, nor use the information he provided for any unlawful practice.
“The Sun abides by all laws and regulations and maintains strict protocols in relation to the obtaining of information from third parties. Strict compliance is in place to cover all our reporting.”
A spokesperson for Harry and Meghan said: “The Duke and Duchess of Sussex feel that today is an important moment of reflection for the media industry and society at large, as this investigative report shows that the predatory practices of days past are still ongoing, reaping irreversible damage for families and relationships.
“They are grateful to those working in media who stand for upholding the values of journalism, which are needed now more than ever before.”