Donald Trump slammed Prince Harry over his "unforgivable" betrayal of Queen Elizabeth II when he took a jab at the Biden administration's handling of the royal's U.S. visa application.

During an interview with Daily Express U.S. Saturday, the former president and current GOP presidential frontrunner claimed that President Joe Biden's administration granted the Duke of Sussex special privileges after he decided to step back as a working royal and move from his home country U.K. to California with his wife Meghan Markle in 2020.

While he claimed that the government has been protecting Prince Harry by keeping his visa application confidential, Trump made it clear that he wouldn't be as "gracious" to the royal if he were reelected as president.

"I wouldn't protect him. He betrayed the Queen. That's unforgivable. He would be on his own if it was down to me," the former president said.

"I think they have been too gracious to him after what he has done," Trump added.

(Photo : David Becker/Getty Images)
Republican presidential candidate and former U.S. President Donald Trump stands on stage during a campaign event at Big League Dreams Las Vegas on January 27, 2024 in Las Vegas, Nevada.

Prince Harry sparked controversy last year after he revealed his past drug use in his bombshell memoir, "Spare."

In the book, which dropped in January 2023, he admitted to having taken cocaine, marijuana, and psychedelic mushrooms when he was younger.

Following his revelation, the conservative think tank Heritage Foundation took the federal government to court in a bid to gain access to immigration documents for Prince Harry.

The organization aimed to determine if the royal disclosed his past drug use before getting his U.S. visa.

(Photo : Andy Stenning - WPA Pool/Getty Images)
Prince Harry, Duke of Sussex arrives for the Coronation of King Charles III and Queen Camilla at Westminster Abbey on May 6, 2023 in London, England.

In its lawsuit, the Heritage Foundation argued that U.S. law "generally renders such a person inadmissible for entry" to the country, the New York Post reported.

The Department of Homeland Security (DHS) had denied the conservative research group's request, saying it "does not find a public interest in disclosure sufficient to override the subject's privacy interests."

During a hearing Friday, John Bardo, a lawyer for the DHS, said that Prince Harry's records should remain private and that his "Spare" revelation was not "sworn testimony or proof" that he took drugs.

"Just saying something in a book doesn't make it true," Bardo said.

The lawyer suggested that it could have been a ploy to "sell books."

(Photo : Getty Images/Joern Pollex)
Prince Harry, Duke of Sussex makes a speech during the closing ceremony of the Invictus Games Düsseldorf 2023 at Merkur Spiel-Arena on September 16, 2023 in Duesseldorf, Germany. (Photo by/Getty Images for Invictus Games Düsseldorf 2023)

Meanwhile, lawyers for the Heritage Foundation cited Prince Harry's comments in a recent interview, the Daily Mail reported.

"American citizenship is a thought that has crossed my mind but certainly is not something that is a high priority for me right now," the Duke of Sussex told "Good Morning America" last week.

According to the Heritage Foundation's legal team, the idea that Prince Harry was potentially seeking U.S. citizenship added to the think tank's case of seeking the release of the royal's records.