Anti-monarchy group Republic said the monarchy is facing “its worst crisis since the abdication in 1936”.
Republic's chief executive, Graham Smith, said the monarchy is “tolerated because of a carefully managed but dishonest image” that has been created over the years.
He said: “The monarchy has just been hit by its worst crisis since the abdication in 1936. Whether for the sake of Britain or for the sake of the younger royals, this rotten institution needs to go.
“Some people will say ‘Well, you would say that’, but this interview has only served to highlight what a lot of people have known for years: the monarchy is rotten to the core and does not reflect British values.
“Most people in the UK don’t give a second thought to the royals, they’re just not that interested.
“The monarchy is tolerated because of a carefully managed but dishonest image that’s been created over the past few decades.”
He said people are now “getting a much clearer picture of what the monarchy is really like”, adding that is “doesn’t look good”.
He went on: “With the Queen likely to be replaced by King Charles during this decade, the position of the monarchy has rarely looked weaker.
“We now need honesty in the monarchy debate that has been sorely lacking until now. Honesty about the democratic alternative, honesty about royal corruption, honesty about costs, tourism and every other bit of nonsense trotted out by royalists for years.
“Britain is better than this. We deserve better than this. The monarchy will always be part of our history. It mustn’t be part of our future.”
During their candid Oprah Winfrey interview, the Duke and Duchess of Sussex hit out at the institution and members of the royal family in a series of astonishing admissions.
Appearing vulnerable at times, the duchess revealed that working for The Firm – as the royal family is sometimes known – ultimately left her feeling that ending her life was an option, and how she had not been protected by the monarchy.
Asked explicitly by Winfrey if she was thinking of self-harm and having suicidal thoughts at some stage, Meghan replied: “Yes. This was very, very clear.
“Very clear and very scary. I didn’t know who to turn to in that.”
A member of the royal family – who both Harry and Meghan refused to identify – was worried about how dark their son Archie’s skin tone might be before he was born.
Meghan told Winfrey there had been “concerns and conversations about how dark his skin might be when he is born”.
Harry suggested his family were jealous of Meghan’s popularity with the public – just as the appeal of his mother, Diana, Princess of Wales, had reportedly been seen as a threat.
And he revealed he has become estranged from his father, the Prince of Wales, saying: “I feel really let down”, but added that he would make it one of his priorities “to try and heal that relationship”.