"I will have not one word said about him on any level, any level," she said of her ex-husband, who she divorced in 1996.
The Duke of York has been named in court documents filed in Florida relating to how prosecutors handled the case against billionaire financier Jeffrey Epstein. The woman in the case has been identified by the press as Virginia Roberts, and she has alleged that she was forced to be intimate with the royal when she was 17 – a minor under US law.
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Sarah, Duchess of York said she will have "not one word" said about Prince Andrew
Buckingham Palace released a statement that adamantly denied the claims, and Sarah told Today host Matt Lauer that they "stand by that denial".
"I want to stand by him, because I know what it feels like to have salacious lies made up about you," she revealed, adding that her former husband is "a great father and humongously good man".
"I won't stand by and let his character be defamed to this level," she said.
Prince Andrew has been described as a "humongously good man" by his ex-wife
The Duchess previously defended Prince Andrew following the allegations which surfaced while she was on a skiing holiday in Verbier, Switzerland. When asked by the Daily Mail if she was sticking by her former husband, the 55-year-old confirmed that she would and described him as "the greatest man there is".
"The York family is a tight unit. We’ve always been a tight unit. He is the greatest man there is. It was the finest moment of my life in 1986 when I married him. He is a great man, the best man in the world," she said.
Buckingham Palace released a series of formal statements which said the claims were "false and without foundation".
The Prince is expected to go ahead with his scheduled public engagement on 21 January, hosting a reception for foreign ministers on behalf of the British government.