NEW YORK (BLOOMBERG) - Mr Donald Trump has asked a New York state judge to throw out a lawsuit in which his niece accused the President and his siblings of conspiring to defraud her of tens of millions of dollars.

Ms Mary Trump, the daughter of Mr Trump's late older brother Fred Jr, waited too long to bring her allegations that she was swindled out of her stake in the family businesses, Mr Trump said in a filing on Wednesday (Dec 23) in Manhattan.

Moreover, she already settled with the family over similar claims in 2001, according to Mr Trump.

"Plaintiff makes outlandish and incredulous accusations in her complaint, which is laden with conspiracy theories more befitting a Hollywood screenplay than a pleading in a legal action," Mr Donald Trump's request to dismiss the case said.

"(The) plaintiff even uses the thematic structure of a play to contrive a decades-long sinister plot in which she claims her aunt and uncles conspired with reputable lawyers, appraisers and other professionals to defraud her."

Ms Mary Trump's book, Too Much and Never Enough: How My Family Created the World's Most Dangerous Man, came out in July, after the Trump family failed to block publication because the tell-all book allegedly breached a confidentiality agreement.

The book sold 1.35 million copies in the first week after it was published, according to Simon & Schuster.

Mr Trump's sister, Ms Maryanne Trump Barry, also asked to have the claims dismissed in a separate filing.

Ms Mary Trump's suit is seeking to undo the settlement Maryanne said she entered into almost two decades ago.

In her request to have the lawsuit dismissed, Maryanne said the central allegation in the lawsuit - that Mary's aunt and uncles stole money from her by using bogus loans and other methods - appears to have been lifted from a New York Times report based on the same set of records that Mary had for 20 years.

The lawsuit "offers nothing more than conclusory allegations" that the Trump siblings "concealed the alleged fraud, and her own public statements contradict any claim that she could not have discovered the alleged fraud years earlier", Ms Maryanne Trump Barry said in the filing.

Mary claims Mr Donald Trump, Maryanne and their late brother Robert failed to follow through on a pledge to "watch over her interests as fiduciaries" after she inherited minority interests in the family business following the death of her father Fred Trump Jr, the President's older brother.

She claims the President and his siblings gave her fraudulent valuations as part of a 2001 settlement agreement over the wills and "forced her to sign".

The family members all signed a confidentiality agreement as part of the settlement.