LONDON (AFP) -- Suicidal thoughts, a racist relative and an heir-to-the-throne trapped by tradition -- Prince Harry and his wife Meghan have lifted the lid on life inside Britain's royal family with an explosive interview that reverberated around the world.

The two-hour sit-down with Oprah Winfrey by the Duke and Duchess of Sussex was the most startling since Harry's late mother Princess Diana made her own bombshell revelations in 1995, and triggered similar questions about the ability of Queen Elizabeth II's family to weather the storm.

Harry described feeling "really let down" by his father Prince Charles, who had stopped taking his phone calls for a time. Both Charles -- the queen's heir -- and Harry's elder brother William were "trapped" by the conventions of the monarchy.

"They don't get to leave. And I have huge compassion for that," Harry said in the interview broadcast on CBS Sunday night, explaining the couple's dramatic exit from royal life last year, which has now seen them stripped by the queen of their honorary titles and patronages.

Meghan, a mixed-race former television actress, described herself as "naively" unprepared for life in the pressure cooker of the royal family.

But she said she was denied help for a mental health crisis, targeted by lies in an incident involving her sister-in-law, and there was even official concern about the skin colour of her unborn son.

"I... just didn't want to be alive anymore. And that was a very clear and real and frightening constant thought," she told Winfrey, describing the impact of vitriol from hostile tabloids in Britain and social media.

Asked if she had had suicidal thoughts while pregnant with son Archie, Meghan replied: "Yes. This was very, very clear."

Meghan, 39, also told of "concerns" about "how dark" Archie's skin would be, saying Harry revealed to her conversations over their baby's appearance, as well as the security he would be entitled to, ahead of his birth on May 6, 2019.

The couple both declined to name the royal involved but Winfrey said Monday that Harry had told her the queen, 94, and her 99-year-old husband, Prince Philip, were not part of the conversations.

Racism

The revelations have triggered a storm of reaction on both sides of the Atlantic, particularly the explosive claims about racism, opening up a wider debate about prejudice in British society.

Harry himself has faced accusations of using a racist slur against a former military colleague, and of wearing a Nazi soldier's uniform at a fancy dress party.

He has said Meghan had made him confront the issue and since vowed to tackle institutional racism. The couple have been outspoken supporters of the Black Lives Matter movement.

Anti-monarchy group Republic said the revelations showed the institution was "rotten to the core" and facing "its worst crisis since the abdication in 1936", referring to Edward VIII's decision to step down to marry an American divorcée.

Meghan won wide-ranging support, including from tennis ace Serena Williams and Bernice King, daughter of the civil rights leader Martin Luther King Jr.

The White House said Monday that it took "courage" for the couple to speak out.

"For anyone to come forward and speak about their own struggles with mental health and tell their own personal story, that takes courage," President Joe Biden's press secretary, Jen Psaki, told reporters.

Amid political calls for a full investigation, UK Prime Minister Boris Johnson -- whose own views during his time as a newspaper columnist have been seen as racist -- refused to comment.

But he told reporters: "I've always had the highest admiration for the queen and the unifying role she plays in our country and across the Commonwealth."

Cast adrift

Criticism of Harry and Meghan has mounted with Prince Philip currently in hospital, and Buckingham Palace last week alleged the duchess had bullied household staff.

Royal author Robert Hardman told AFP that in trying to "set the record straight", the couple had "invited a whole new set of questions."

A snap YouGov poll of 2,111 adults in Britain indicated 47 percent thought the couple's interview was "inappropriate", with 21 percent in favour.

Chris Ship, royal editor at ITV, which airs the interview in Britain on Monday night, said the couple "effectively loaded up a B-52 bomber, flew it over Buckingham Palace and then unloaded their arsenal right above it, bomb by heavily-loaded bomb."

Harry, 36, said the pair, who have secured lucrative deals with Netflix and Spotify, had to find a way to make money as "my family literally cut me off financially".

In one happier revelation, the couple disclosed the gender of their second baby, due later this year. "It's a girl!" Harry and Meghan chimed in tandem.

But it was a rare light-hearted moment.

Wedding for show

Meghan has been portrayed in some British newspapers as headstrong, calculating and spoiled, and the couple reckless and selfish for quitting royal life.

She flatly denied reports -- feasted on by the gossip press -- that she made Prince William's wife Kate cry before her wedding to Harry, saying the reality was the opposite.

But despite Kate apologising, the rumour was allowed to persist, Meghan added, calling the claims "the beginning of a real character assassination" and "a turning point" in her relations with the royal family.

The May 2018 wedding in front of Winfrey and other VIP guests was merely a "spectacle for the world", Meghan revealed.

The couple had actually got privately married three days earlier, by the Archbishop of Canterbury.