Oprah Winfrey's tell-all TV interview with the couple has dragged the royals into the biggest crisis since the death of Harry's mother Diana in 1997, when the family, led by Queen Elizabeth, was widely criticised for being too slow to respond.

In the two-hour show, originally aired on CBS on Sunday evening, Harry also said that his father, heir-to-the-throne Prince Charles, had let him down.

"Worst Royal Crisis in 85 Years," read the front page of the Daily Mirror newspaper, while the Daily Mail's cover asked "What Have They Done?". The Sun columnist Trevor Kavanagh questioned if the interview meant the end for the royals.

"It could hardly be more damaging to the royal family, not least because there is little it can do to defend itself," The Times said in a lead article under the title "Royal Attack".

"The key to the monarchy's survival over the centuries has been its ability to adapt to the needs of the times. It needs to adapt again," The Times said.

Elizabeth, who is 94 and has been on the throne for 69 years, wanted to take some time before the palace issued a response, a royal source said.

Nearly three years since her star-studded wedding in Windsor Castle, Meghan gained sympathy in the United States by casting some unidentified members of the British royal family as uncaring, mendacious or guilty of racist remarks.

She and Harry have also had a torrid relationship with the British press, and in particular tabloids who have been critical of the couple.

For the monarchy, Meghan's bombshell has been compared to the crises over the death of Diana and the 1936 abdication of Edward VIII.

Opponents of the monarchy said the allegations made by Meghan and Harry showed how rotten the institution was.

"Now people are getting a much clearer picture of what the monarchy is really like. And it doesn't look good," said Graham Smith, head of Republic, a campaign group which seeks to abolish the monarchy.

"With the Queen likely to be replaced by King Charles during this decade the position of the monarchy has rarely looked weaker," Smith said.

Some royal supporters cast Meghan, a 39-year-old former US actor, as a publicity seeker with an eye on Hollywood stardom.

But the gravity of the claims has raised uncomfortable questions about how the British monarchy, which survived centuries of revolution that toppled their cousins across Europe, could function in a meritocratic world.

Meghan, whose mother is black and father is white, said her son Archie, who turns two in May, had been denied the title of prince because there were concerns within the royal family "about how dark his skin might be when he's born".

She declined to say who had voiced such concerns, as did Harry. Winfrey later told CBS that Harry had said it was not the Queen or her 99-year-old husband Philip, who has been in hospital for three weeks while the crisis unfolds.

Meghan's estranged father Thomas Markle said on Tuesday he did not think the royal family was racist, and hoped that an alleged remark from a family member about the darkness of the skin of Meghan's son was just a "dumb question".

"The thing about what colour will the baby be or how dark will the baby be; I'm guessing and hoping it's just a dumb question from somebody," Markle told ITV. "It could be somebody asked a stupid question. Rather than being a total racist."

Australian Associated Press