Mary Trump, the niece of Donald Trump, filed a lawsuit against her uncle on Thursday, accusing the US president and other family members of cheating her out of tens of millions of dollars from an inheritance following the death of her father in the 1980s.

The complaint against President Trump, his sister Maryanne Trump Barry, and the estate of his brother Robert Trump, who died on August 15 this year, accused the defendants of "rampant fraud" and civil conspiracy.

She alleges that Donald Trump, Maryanne and their late brother Robert, took control of the real estate empire of their father Fred, who died in 1981 aged 42 after a struggle with alcoholism, and "exploited it to enrich themselves at the expense of everyone around them."

Mary Trump says the family members portrayed themselves as her protectors while secretly siphoning off her stake in the family's real estate holdings.

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First foray in writing, and now in court

The lawsuit, filed in a New York state court in Manhattan, reiterates some of the allegations in Mary Trump's recent book, "Too Much and Never Enough: How My Family Created the World's Most Dangerous Man."

In it she accused the president and the other defendants of doing everything in their power to "squeeze" her out of some of the family estates, including that of her grandfather, Fred Trump Snr, who died in 1999.

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"Fraud was not just the family business — it was a way of life," Thursday's complaint alleges.

In a statement given by her lawyer, Mary Trump said the defendants "betrayed me by working together in secret to steal from me, by telling lie after lie about the value of what I had inherited, and by conning me into giving everything away for a fraction of its true value."

jsi/msh (Reuters, dpa)