The future king is putting his foot down when it comes to disgraced relative Sarah “Fergie” Ferguson,  an insider tells In Touch.

After a slew of emails were released revealing just how tight the former Duchess of York used to be with late convicted pedophile Jeffrey Epstein, she’s no longer welcome around the royals — and Prince William has allegedly led the charge to ban his onetime aunt.

“William’s made it clear to everyone that Sarah is persona non grata,” confirms the insider. “He doesn’t want to ever see her face again.”

In 2008, Epstein was convicted of soliciting a minor for prostitution.

More than a decade later, the 66-year-old died as he awaited trial on sex trafficking charges.

While Ferguson had denied any misconduct and publicly distanced herself from the fallen financier — claiming via a representative that she was “taken in” by Epstein’s “lies” — correspondence between the pair seemingly tells another story.

Messages that were recently made public by the U.S. Department of Justice detailed how she sought advice from Epstein on building a women’s empowerment brand, and efforts were even made to make him a majority stakeholder, Sky News reports.

Meanwhile, The Telegraph notes that Fergie and her daughters, Princess Beatrice and Princess Eugenie, visited the registered sex offender in Florida just days after his 2009 release from prison.

The following year, the redhead, 66, asked the man whom she called “the brother I always wished for” to find her “pretty” 22-year-old goddaughter a job and housing in New York.

“Sarah has always claimed that she cut ties with Epstein, that she was only close to him before she realized the sort of creep he was, but the truth is finally out and it’s beyond damning,” says the source. “Things are looking more depraved by the day.”

Though rumors have circulated that Ferguson is merely waiting for the dust to settle so that she can return to the royal fold, the insider insists she has zero chance of redeeming herself with William, 43.

Last year, the children’s book author and ex-husband Andrew Mountbatten Windsor were stripped of their royal titles over their links to Epstein — despite both repeatedly denying any wrongdoing.

“Fergie and Andrew are so radioactive at this point that they could topple the whole monarchy,” dishes the insider. “But William is hellbent on making sure that doesn’t happen, and that means keeping both Andrew and Sarah far, far away.”