Prince Harry left out revelations about his family in his memoir, saying he did not want "the world to know because I don't think they would ever forgive me," according to an interview published by the Daily Telegraph on Friday.

The prince told the UK broadsheet that he has enough material to write another book, mostly focussed on his relationship with his brother Prince William and father King Charles III, in comments likely to further unsettle the royal family.

"The first draft was different. It was 800 pages, and now it's down to 400 pages," he said of his book "Spare".

"It could have been two books, put it that way. And the hard bit was taking things out.

"There are some things that have happened, especially between me and my brother, and to some extent between me and my father, that I just don't want the world to know. Because I don't think they would ever forgive me," he added.

The rogue prince said the media had a "tonne of dirt about my family" but that they "sweep it under the carpet for juicy stories about someone else".

After months of anticipation and a blanket publicity blitz, Harry's book "Spare" went on sale Tuesday as royal insiders hit back at his scorching revelations.

The royal family have maintained a studied silence as painful details from the book and a round of pre-publication TV interviews have piled up.

In "Spare", Harry portrays his father, 74, as emotionally crippled, the victim of brutal childhood bullying.

But among the many contradictions in the book, Harry also characterises the king as a doting father, who favours strong French aftershave and conducts headstands in his underwear to alleviate polo-induced back pain.

In his Telegraph interview, Harry said he was airing his grievances in public not to "collapse" the royal family but because he had a "responsibility" to reform it in order to protect Prince William's children.

William, he said, "has made it very clear to me that his kids are not my responsibility."

The book comes on the back of the six-hour Netflix docuseries "Harry & Meghan".

A YouGov poll on Monday found that 64 percent of Britons now have a negative view of the once-popular prince -- his lowest-ever rating -- and that Meghan also scores dismally.

They may also be straining public interest in Meghan's homeland, according to the New York Times.

"Even in the United States, which has a soft spot for royals in exile and a generally higher tolerance than Britain does for redemptive stories about overcoming trauma and family dysfunction, there is a sense that there are only so many revelations the public can stomach," its former London correspondent Sarah Lyall wrote.