Mary Trump says she heard president use n-word and antisemitic slurs as White House claims she's lying

'This is a book of falsehoods, plain and simple. The president doesn't use those words,' White House spokeswoman says

The president's niece Mary Trump said late Thursday she has heard him use the n-word and anti-Semitic slurs over the years - as new figures show fewer than 30 per cent of Americans trust her uncle to handle race relations.

Ms Trump, who is making the media rounds pushing a new book that argues her uncle is the "most dangerous man in the world," made the explosive claims during an interview with MSNBC's Rachel Maddow. She made similar charges in the book.

Ms Maddow asked if Ms Trump heard the now-president use the n-word "specifically."

"Of course I did," Mr Trump's niece responded.

"And I don't think that should surprise anybody given how virulently racist he is today," Ms Trump added.

The MSNBC host continued to press, asking: "Have you heard the president use the 'n-word?'''

"Yeah," Ms Trump replied.

Ms Maddow again: "And anti-Semitic slurs specifically?"

"Yes," said the president's niece.

The White House accused Ms Trump of lying.

"This is a book of falsehoods, plain and simple," spokeswoman Sarah Matthews said Friday. "The president doesn't use those words."

Ms Trump's allegations come as fewer and fewer Americans trust what the president says or believe he is better suited to handle race relations than former Vice President Joe Biden, the presumptive Democratic presidential nominee.

Asked "who do you trust more to handle each of the following? Race relations," 50 per cent of respondents to a recent Politico-Morning Consult poll chose Mr Biden. Just 29 per cent selected the president.