After his first bid to halt publication of a book by the president’s niece was thrown out of court, Donald Trump’s brother is asking another court to suppress the tell-all tome.

Robert Trump’s lawyers say Mary Trump signed a legal settlement with several family members nearly two decades ago that included a confidentiality clause barring her from publishing the book.

They said the deal included a “substantial financial settlement” for Mary Trump.

Surrogates Court Judge Peter Kelly in New York City dismissed Robert Trump’s request for an injunction on Thursday, saying the court lacked jurisdiction to hear the case.

Robert Trump’s lawyers filed another injunction request Friday in Supreme Court in Dutchess County, New York, where Robert Trump lives.

Mary Trump’s book details the dark secrets of a “toxic family”.

“Mary Trump reaped the rewards of the agreement for 20 years, and now seeks to breach the agreement by cashing in on a ‘tell-all” book’, Charles Harder, lead lawyer for Robert Trump, said in a statement on Saturday.

“The enforcement of voluntary contracts is a pillar of our legal system. This private dispute has nothing to do with the First Amendment.”

The settlement agreement related to the will of Donald Trump’s father, New York real estate developer Fred Trump.

Mary Trump is the daughter of Fred Trump Jr, the president’s elder brother, who died in 1981. An online description of her book, Too Much and Never Enough: How My Family Created the World’s Most Dangerous Man, says it reveals “a nightmare of traumas, destructive relationships, and a tragic combination of neglect and abuse”.

Her lawyer, Theodore Boutrous, said in a statement that the new legal filing “is yet another baseless attempt by the Trump family to obtain an unconstitutional prior restraint to block core political speech relating to the President”.

Published accounts of the book’s contents say it contains an “insider’s perspective” of “countless holiday meals” and family interactions and family events, along with personal observations by Mary Trump, a psychologist, about her “supposedly toxic family,” according to court papers.

In court papers, lawyers for Robert Trump said the book also has been promoted as containing insight into the “inner workings” of the Trump family and allegations that the late Fred Trump and the president neglected Mary Trump’s father, “supposedly contributing to his early death”.

-with AAP