Prince Harry was savagely branded an "idiot" by John Lennon's son Sean Ono Lennon.
Ono Lennon, 48, sparked fury among the royal's fans when he posted a joke about his book Spare, writing: "My long awaited review of Prince Harry’s autobiography is two words. 'Spare Me.'"
He doubled down on his criticism of Harry as he was slammed on social media.
The musician also recalled meeting the late Princess Diana's youngest son.
Ono Lennon wrote: "Actually I am aware [that we have things in common]. We met once. That was before I realized he was an idiot."
Defending his initial post, the 48-year-old added: "It was a pun. But he deserves to be mocked after that todger episode. He’ll be fine."
The "todger" phrase is a reference to Prince Harry writing in his memoir Spare that he treated his frostbitten penis, which he called his "todger", with his late mother's favourite lip cream.
As social media users continued supporting Harry, mentioning the tragedies he has been through, Ono Lennon stood by his decision to mock the royal.
He said of Harry's past: "That is very sad. I don’t hold any of that against him.
"It’s the stupidity that bothers me."
He continued: "Just because I made a joke does not mean I don’t empathize with him. I do actually.
"Also why I’m very disappointed with his outlook. I was hoping he’d be smarter."
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Ono Lennon also replied to a Sussex fan who suggested that John Lennon's son was jealous of Harry being a best-selling author.
He said: "I mean, I don’t care but I did win an Oscar this year so…I think I’m doing okay."
Ono Lennon won an Oscar in March for Best Animated Short Film, which was awarded for "War Is Over! Inspired by the Music of John & Yoko".
The 48-year-old co-wrote the film with director Dave Mullins.