Donald Trump and niece, Mary Trump

US President Donald Trump’s niece has filed a lawsuit, accusing him and two family members of fraud and conspiracy.

Mary Trump alleges that Mr Trump, his sister Maryanne Trump Barry and brother Robert Trump, who died in August, cheated her out of an inheritance.

Ms Trump, who in July released a tell-all memoir about the president, is seeking to recover millions of dollars she claims to have lost.

Neither Mr Trump nor his siblings have publicly commented on the issue.

Donald Trump

Mary Trump’s memoir, Too Much and Never Enough: How My Family Created the World’s Most Dangerous Man, describes the president as a “narcissist” who now threatens the life of every American.

The White House rejects the claims made in the book, and the Trump family unsuccessfully sued to try to block it.

It says President Trump and his siblings should be tried on eight counts, including fraudulent misrepresentation and concealment, and civil conspiracy.

The Trump family siblings
An undated photo of the Trump siblings, from left to right: Robert, Elizabeth, Fred (Mary Trump’s father), Donald and Maryanne

The lawsuit says that Mary Trump “inherited valuable minority interests in the family business” after the death of her father Fred Trump Jr in 1981, and that “Donald, Maryanne, and Robert committed to watch over her interests as fiduciaries”.

“They lied. Rather than protect Mary’s interests, they designed and carried out a complex scheme to siphon funds away from her interests, conceal their grift [fraud], and deceive her about the true value of what she had inherited,” the court document says.

Mary Trump, 55, is a US psychologist, businesswoman and author.