US President Donald Trump’s niece says her uncle is “criminal, cruel and traitorous” and belongs in prison after he leaves the White House.

Mary Trump, a psychologist, author and outspoken critic of her estranged relative, rejects the notion that putting a former president on trial would deepen the nation’s political divisions.

“It’s quite frankly insulting to be told time after time that the American people can handle it and that we just need to move on,” Mary Trump told The Associated Press in an interview this week.

“If anybody deserves to be prosecuted and tried, it’s Donald,” she added.

“(Otherwise) we just leave ourselves open to somebody who, believe it or not, is even worse than he is.”

Asked about her comments, a spokesman for Donald Trump’s presidential campaign emailed a one-sentence response: “Did she mention she has a book to sell?”

Mary Trump, the daughter of the president’s elder brother, Fred Jr., announced this week she is writing a follow-up to this summer’s scathing bestseller about her uncle, Too Much and Never Enough, How My Family Created The World’s Most Dangerous Man.

Her new book, The Reckoning, from publisher St. Martin’s Press won’t be out until next July. It will trace what she says is America’s collective trauma from its founding on the backs of enslaved Africans to the burgeoning economic and mental health impacts of the coronavirus pandemic.

Tweet from @MaryLTrump

Mary Trump’s critical writings come amid legal fights with her family.

Her uncle, Robert Trump, sued to block Too Much and Never Enough from hitting store shelves, citing a family agreement not to publish stories about core family members without their approval, but a court rejected that.

In September, Mary Trump sued the president, Robert Trump and their sister Maryanne Trump Barry, a retired federal judge, alleging that they cheated her out of millions of dollars while squeezing her out of the family business. Robert Trump died in August and the lawsuit is pending.

When her book about the family was published in July, Mr Trump tweeted that Mary Trump was “a seldom seen niece who knows little about me, says untruthful things about my wonderful parents (who couldn’t stand her!) and me,” and violated a non-disclosure agreement.

Tweet from @realDonaldTrump

The announcement of Mary Trump’s second book came as her uncle continued to falsely insist he won re-election but that the vote was rigged in favour of Democratic rival Joe Biden.

The President has spent the better part of the last month complaining about the results, dispatching a band of lawyers led by former New York City Mayor Rudy Giuliani to mount futile legal challenges.

Mary Trump said the president’s post-election behaviour “makes perfect sense,” given his personality, psychology, and lifelong disdain for losers.

“This is somebody who’s never won legitimately in his life,” she said.

“But he’s never lost either. Because in his view, winning is so important and he always deserves to win that it’s OK to lie, cheat and steal.”

Mary Trump acknowledges that she has seen the president only sporadically over the last 20 years – she wrote in Too Much and Never Enough that he invited her to a family dinner at the White House in 2017 – but, she argues, “he hasn’t changed at all”.

“I’m essentially looking at the same person I knew when I was growing up,” she said.

Donald Trump is facing at least one pending criminal investigation, a probe into his business dealings by the Manhattan district attorney that has been slowed by a legal fight over access to his tax returns.

No former president has ever been arrested after leaving office, but Mary Trump argues that shielding powerful people from punishment has historically harmed the country.

“I think it would be a tragedy if Donald and everybody who’s enabled him and committed crimes with him is not held accountable,” Mary Trump said.

“It would make it impossible for this country to recover in the long term.”

-AP