Donald Trump has filed a $10bn (£7.5bn) lawsuit against the Wall Street Journal’s parent company Dow Jones and its owner Rupert Murdoch over claims that he wrote a “bawdy” note to sex offender Jeffrey Epstein.

The US president claims the publication slandered him and violated libel laws in an article alleging that a birthday greeting bearing Trump’s name was sent to the late financier in 2003, before he was charged with sex crimes.

Trump said the note, which the paper reported he had sent for Epstein’s 50th birthday, is “fake”.

It came as the US justice department asked a judge to unseal material related to Epstein, following intense criticism of the Trump administration’s handling of the case.

Trump said on social media: “We have just filed a powerhouse Lawsuit against everyone involved in publishing the false, malicious, defamatory, fake news ‘article’ in the useless ‘rag’ that is, The Wall Street Journal.

“I hope Rupert and his ‘friends’ are looking forward to the many hours of depositions and testimonies they will have to provide in this case.”

He said the newspaper and Murdoch – with whom Trump has had an up-and-down relationship for decades – were warned they would be sued if they printed the article.

A Dow Jones spokesperson said in a statement to the BBC: “We have full confidence in the rigor and accuracy of our reporting, and will vigorously defend against any lawsuit.”

Murdoch, who was seen on Sunday attending the Fifa Club World Cup with Trump, founded a media empire which is credited by some with helping propel the president to the White House.

According to the Wall Street Journal, a letter bearing Trump’s name “contained several lines of typewritten text framed by the outline of a naked woman, which appears to be hand-drawn with a heavy marker”.

“Inside the outline of the naked woman was a typewritten note styled as an imaginary conversation between Trump and Epstein, written in the third person,” the paper reported.

It reportedly contained a joking reference that “enigmas never age” and allegedly ended with the words: “A pal is a wonderful thing. Happy Birthday – and may every day be another wonderful secret.”

Trump denied writing the note after the article was published on Thursday, posting: “These are not my words, not the way I talk. Also, I don’t draw pictures.”

The US justice department request concerns transcripts from the grand jury involved in the government’s 2019 sex trafficking case against Epstein, materials that are typically kept secret and protected by law.

On Thursday, Trump ordered Attorney General Pam Bondi to seek the release of documents related to Epstein’s secretive grand jury testimony.

The justice department formally made the request to a judge in New York, arguing the materials related to the case – where he was charged with trafficking dozens of girls as young as 14 – “qualify as a matter of public interest”.

The department is also asking for disclosures in the case of his associate Ghislaine Maxwell, who was convicted in the child sex trafficking conspiracy.

A grand jury – a panel of people who vet whether there is enough evidence to charge a person with a crime – can hear from confidential informants and those whose identities are protected for their safety. Materials in a grand jury are typically kept secret under the law, but a judge can unseal documents if they decide public interest outweighs the need for such legal protections in a case.

Either way, it is unclear when or if the documents will be released, or if they contain many of the details Trump’s supporters have been demanding to see.

The developments on Friday came amid a turbulent week for the president as some of his most loyal supporters demanded more transparency and public disclosure in the Epstein case.

Some Trump loyalists have even called for Attorney General Bondi to resign after she reversed course on releasing certain documents related to Epstein.

Chad Bianco, a Republican sheriff running for California governor, told BBC News that Trump’s handling of the Epstein files was not what he was “expecting” and that “millions” of his followers are disappointed.

“We feel like we’re being talked down to like stupid children,” he added.

Meanwhile, members of Congress are pushing to pass a “discharge petition” that would force Bondi to release a broad range of materials that the justice department has related to Epstein.

The effort has brought together some of Congress’s fiercest opponents, including Republican Marjorie Taylor Greene and Democrat Alexandria Ocasio-Cortez, who are both signed on as supporters.