Prince Harry told the late Queen Elizabeth to “suck it up” when she expressed doubts over Meghan Markle’s suitability for marriage, a royal author claims.

Controversial writer Lady Colin Campbell claims a friend of the monarch told her about the interaction – and says despite never hearing the phrase before, she “instantly understood” what it meant.

The 74-year-old socialite, known as Lady C, made the claim in The Scandal Mongers podcast, adding that Harry told Elizabeth and Prince Phillip that “if they did not agree to the marriage they would be accused of racism”. She also alleges that Phillip told Harry “we do not marry actresses, we ‘step out’ with them”.

When approached for comment, Lady C doubled down on her claims, saying: “The Queen tried to intervene, and he told her that if she didn’t allow the marriage she would be accused of racism and would have to ‘suck it up’. She said she had never heard the expression before but understood as soon as she heard it.

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“His grandfather told him one does not marry actresses, one ‘steps out’ with them. It was a very plain way of saying you can sleep with them but they’re not suitable for marriage. There were tremendous concerns as to her suitability as an individual and to her attitude and her modes of expression and behaviour All of which turn out to have been absolutely accurate.”

Lady C, who has written seven unauthorised books about the Royal Family, released an update to her book ‘Meghan and Harry: The Real Story’ on April 4. The book claims to cover “what happens when a vulnerable male, raised in the traditions of the Old World… falls head over heels in love with a steely and ambitious doyenne of the New”.

The author claims Harry told his grandparents they “would be accused of racism” if they did not accept the marriage. But she says “the objections had nothing to do with race, they had to do with Meghan herself”.

Elaborating on her opinion, Lady C said: “There were two reasons the Queen allowed the marriage. The main reason was Meghan was a woman of colour – had Meghan been white they would have never allowed that marriage. Most citizens of the Commonwealth are not white – for first time they could see a person of colour had been welcomed into the Royal Family.

“The second reason they agreed to the marriage was because Meghan could control Harry – who up until then had been totally uncontrollable. It was unusual for Harry to have exploded so particularly to his grandparents, but Harry has always been explosive.

Lady C appeared on I’m A Celeb… in 2015

“He’s always been explosive and unmanageable – this is something I and people of my world have known all along. To the best of my knowledge he’d never behaved like that to his grandparent’s before where his volcanic side just spewed forth, but it certainly happened in this instance I was told.”

Lady Colin Campbell is a British Jamaican author, socialite and television personality. As well as writing books on the royals, she has appeared on I’m a Celebrity… Get Me Out of Here! and Celebs Go Dating.