The alleged “nasty” remarks made by Prince Andrew about Kate Middleton have reportedly ignited his ongoing conflict with his nephew, Prince William, as noted by a royal biographer.

The 65-year-old Duke of York has been distanced from both Prince William and Prince Harry for several years, with recent accounts indicating that the 43-year-old Prince of Wales views his uncle as a “problem.”

Andrew Lownie, a prominent royal author, claims in his latest biography, “Entitled: The Rise and Fall of the House of York,” that Andrew has made numerous “rude” and “unkind” comments about the Princess of Wales.

Lownie added that the alleged remarks came from a place of jealousy, as the duke was envious that Catherine had become a key figure of the Firm following the death of Queen Elizabeth II.

The alleged comments had resulted in the breakdown of his relationship with the future king, Lownie claims.

“I can’t see how anyone could make unkind comments about Kate when she’s been the family’s saving grace,” Lownie told Radar Online.

“It surprised me, but people do get jealous,” he added. “I’d have thought Prince Andrew would respect William as future king though” than to be “nasty about his wife.”

It’s not known exactly what was said about the future queen; however, Lownie suggested that the remarks prompted William to turn his back on his scandal-scarred uncle.

What’s more, he added that William had grown increasingly frustrated with his uncle over the past few years.

“William has a very strong sense of public duty and is doing his best to keep the show on the road,” Lownie said. “He’s all about doing things the right way and has enough on his plate without having to think about his uncle.”

“Everyone is pulling together — Charles, Anne, Edward, William and others — but the whole side has been let down by Prince Andrew,” he added.

Indeed, Andrew’s fate within the monarchy had been reportedly decided by William already.

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Insiders claimed that the duke will not be returning as a working member of the royal family under William’s reign, as he and Kate reportedly see Andrew as a “risk” and “threat” to the Firm — given his previous connections to registered sex offender Jeffrey Epstein and alleged Chinese spy Yang Tengbo.

Additionally, Lownie spoke to sources that suggested William will be eager to evict Andrew and his ex-wife, Sarah Ferguson, from the Royal Lodge, where the pair have lived since 2004.

“He [William] also loathes Sarah, Andrew’s ex-wife, and can’t wait for the day when his father throws them both out,” a source is quoted in the book.

“If Charles doesn’t, I guarantee you the first thing William does when he eventually becomes king is to get them evicted.”

The Post has reached out to Kensington Palace and Andrew’s reps for comment.