John Lennon's son Sean has blasted Prince Harry, Duke of Sussex, as an 'idiot' in a belated review of his tell-all memoir.

Lennon bashed the royal's book Spare on social media, giving the January 2023 release a scathing critique.

"My long-awaited review of Prince Harry's autobiography is two words. 'Spare Me,'" the musician joked via X.

When fellow social media users came to the Duke's defence, Sean doubled down on his negative review.

"I do empathise with him generally. But the way he whines and wangs on about things is really too much," he wrote. "I'm just having a little fun. I think he's earned some mockery. (I'm sure I have as well)."

When one fan wrote that writing Spare took "courage", Lennon joked that the particular revelation about Harry's frostbitten penis certainly did.

The songwriter noted that while he is aware of what he and the Duke of Sussex have in common, he considers Harry an "idiot" and a "buffoon".

He tweeted, "I'm very disappointed with his outlook. I was hoping he'd be smarter."

Lennon also clapped back at claims that he "based his whole life on his father's success", pointing out that he "did win an Oscar this year" and is doing "OK" for himself.

The musician is John Lennon and Yoko Ono's only child, born five years before the late Beatle was shot and killed in New York in 1980.