Britain's royal family was under pressure on Tuesday to respond to Prince Harry and his wife Meghan's claims of racism, triggering a crisis for the institution not seen since the time of his late mother, Diana.

The couple set off a whirl of speculation about the identity of the senior royal who asked how dark their child's skin would be before he was born.

Meghan, whose mother is black and father is white, also spoke about how she had suicidal thoughts but failed to get any support during her time in the royal family.

The racism claims left interviewer Oprah Winfrey open-mouthed but have so far not led to any official response from Buckingham Palace, which newspapers reported had been left in turmoil.

The Daily Mail, which devoted 25 pages of coverage to the "toxic" claims, headlined its front page "What have they done?"

The Times newspaper said Harry's grandmother, Queen Elizabeth II, wanted more time to consider her reply.

'Blowing up his family'

Harry and Meghan's claims have been likened to a bomb being dropped on Britain's most famous family and one of the country's most revered institutions.

Attempts have been made to draw in Prime Minister Boris Johnson, who has himself been accused of racism during his time as a newspaper columnist.

But he refused to comment, even as political calls mounted for a full inquiry and prompted the White House and former US secretary of state Hillary Clinton to comment.

Zac Goldsmith, a junior British foreign minister and close ally of Johnson, however, said former army captain Harry was "blowing up his family".

The level of controversy about the royals has not been seen since the 1990s, during the very public collapse of the marriage of Harry's parents.

His mother, princess Diana, collaborated with the author Andrew Morton in a revealing 1992 biography and gave a bombshell BBC television interview in 1995.

In it, she said both she and her husband, Prince Charles, had been unfaithful, how he was unfit to be king, and that she felt isolated, struggling with self-harm and bulimia.

Morton said on Monday evening that Harry and Meghan's claims would "shudder down through the generations in the same way that Diana's did".

But Meghan's estranged father Thomas Markle defended the royals, saying he hoped the skin tone comment was "just a dumb question".

"It could just be that simple, it could be somebody asked a stupid question, rather than being a total racist," he told Britain's ITV.

Millions of views

Just over 17 million viewers watched Winfrey's two-hour interview with Harry and Meghan on US broadcaster CBS on Sunday night.

More than 11 million people tuned in to watch it in full on ITV in Britain on Monday night, the channel said.

The couple dramatically quit royal life last year and now live in California with their young son, Archie, and are expecting their second child, a daughter, in the summer.

Harry, 36, has admitted his mother's death in Paris in 1997 -- in a high-speed car crash as she tried to flee paparazzi photographers -- has affected his mental health and coloured his view of the media.

The Society of Editors, a guild of senior British newspaper journalists, however rejected his assertion the UK media was bigoted in its coverage of the couple.

Their comments about the suffocating strictures of royal life and claims of unwavering attitudes have wider implications for the monarchy itself -- and what it represents.

Black Lives Matter protests in Britain last year prompted calls for a reassessment of the legacy of the British Empire headed by the queen and her ancestors.

Global impact?

Neither the queen, now 94, and her 99-year-old husband, Prince Philip, made the racist comment, Winfrey told CBS.

But it could still be damaging, as the monarch is head of the Commonwealth, an organisation comprising 54 mainly former British colonies, many of them in Africa, and 2.4 billion people -- nearly a quarter of the world's population.

Since the queen came to the throne in 1952, mass immigration has transformed Britain from a predominantly white country to one in which more people class themselves as British-Asian, black-British or of mixed race.

The historian and broadcaster David Olusoga said Harry and Meghan's claims were "not just a crisis for the royal family -- but for Britain itself", he wrote in The Guardian.

Harry himself has faced accusations in the past of using a racist slur against a former military colleague and was once pictured wearing a Nazi soldier's uniform at a fancy-dress party.

But he has said meeting Meghan, 39, had made him confront the issue, and he is now championing projects to tackle racism.

A snap YouGov poll of 2,111 Britons before the broadcast on Monday indicated 47 percent thought the couple's interview was "inappropriate", with 21 percent in favour.