Lawyers for Melania Trump on Thursday filed suit for $150 million (€133m) damages against the Daily Mail in Maryland state court.
The wife of Republican presidential nominee Donald Trump is also suing a blogger, Webster Tarpley, from the state in question.
In a statement, Mrs Trump's lawyer, Charles Harder, said: "These defendants made several statements about Mrs Trump that are 100 per cent false and tremendously damaging to her personal and professional reputation [and] broadcast their lies to millions of people throughout the US and the world - without any justification.
“Their many lies include, among others, that Mrs Trump supposedly was an ‘escort’ in the 1990s before she met her husband. Defendants’ actions are so egregious, malicious and harmful to Mrs Trump that her damages are estimated at $150 million.”
The suit was filed in Montgomery County, in suburban Washington DC, in response to articles published in August by the Daily Mail which reported rumours that Mrs Trump worked as an escort in the 1990s.
Last month, announcing that Mrs Trump was considering a suit, her lawyer called those rumours “100 per cent false”.
The Daily Mail article also contained allegations that Mrs Trump came to New York a year earlier than she has claimed, raising issues about her immigration status. Mrs Trump denied a story in Politico in which questions about her immigration status were first reported.
The lawsuit noted that while the article in question had been removed from the Daily Mail's website, the newspaper had yet to apologise or formally retract. The Mail included a retraction of the story in its Friday UK print edition.
“We did not intend to state or suggest that these allegations are true,” the newspaper said, “nor did we intend to state or suggest that Mrs Trump ever worked as an ‘escort’ or in the ‘sex business’.”
It added that its article had included denials from a Trump spokesperson and the owner of the modelling agency in question, and said it regretted “any such misinterpretation”.
The retraction was also posted online. "The Daily Mail newspaper and MailOnline/DailyMail.com have entirely separate editors and journalistic teams," it added.
"In so far as MailOnline/DailyMail.com published the same article it wholeheartedly also retracts the above and also regrets any such misinterpretation."
Asked if the retraction would affect the suit, Mr Harder replied: “It does not.”
Tarpley’s blogpost, which has been retracted, claimed, per the suit, that “it is widely known Melania was not a working model but rather a high-end escort” and that she had a “mental breakdown” after a plagiarism controversy over her speech to the Republican national convention in Cleveland in July.
Mr Harder is best known for representing Hulk Hogan in the lawsuit that bankrupted Gawker Media and forced its sale to Univision last month. That suit was funded by the Silicon Valley billionaire Peter Thiel, a vocal Trump supporter.
Steve Klepper, an appellate lawyer for the Baltimore law firm Kramon & Graham, said the inclusion of a blogger in the suit indicated legal manoeuvring.
He said: “Anytime you have a filing that adds a minor in-state defendant, it’s a flag that they were joined to prevent removal to federal court. And as we know, Donald Trump has not been having been the best luck in federal court recently.”
Mr Klepper pointed to a Maryland defamation statute that might provide a basis for Melania Trump’s suit. It reads: “A single or married woman whose character or reputation for chastity is defamed by any person may maintain an action against that person.”
He added, however: “Montgomery County has possibly the highest-percentage college education jury pool in the whole country and I cannot see how the jury pool would be good for [MELANIA TRUMP].”
News of the lawsuit came 68 days before the election, on the day Donald Trump pledged to promote “patriotism” in schools and a day after he gave a hardline immigration policy speech, hours after striking conciliatory notes on the topic in a meeting with Mexican president Enrique Peña Nieto.
The Republican nominee, who has consistently trailed Hillary Clinton in the polls, has developed a combative relationship with the media, blacklisting a number of news outlets and pledging to pass stricter libel laws if elected.
A Trump campaign spokesperson said: “We do not have anything in addition to the Harder statement.”
The Daily Mail responded to a request for comment by pointing to its online and print retractions.