David Cameron’s sister-in-law has claimed that an ex-boyfriend’s father tore her clothes off on a family holiday when she was in her teens.

Emily Sheffield, the younger sister of Samantha Cameron, said the man and his friend removed her top in a swimming pool as a ‘jolly jape’ while her then-boyfriend ‘egged them on’.

Miss Sheffield, the former deputy editor of British Vogue, described sexual harassment as ‘endemic’ and called for change.

She recounted her own experience, after going on holiday with a boyfriend and his family. ‘A few days in, his father and his middle-aged friend, probably both 50, decided it would be a jolly jape to strip me in the pool. 

'The man’s wife walked inside the villa, my boyfriend egged them on from the poolside. I fled with my top removed.’

The 44-year-old also said an unnamed male boss, 25 years her senior, asked if she would ‘**** him’ during a lunch meeting. 

‘Recovering from my initial shock, I said no, naturally,’ she wrote in the London Evening Standard. ‘He countered with a long explanation of how I would be a failure in my career. Miss Sheffield, who is married to actor Tom Mullion, said another boyfriend ‘exaggerated everything we had done sexually’ to his friends after they split up.

‘None of these experiences left me hurt – mostly angry. I could continue with more tales, as could most women. The endless revelations prove that the above, and much worse, is still happening.’

However, despite detailing her own treatment, Miss Sheffield warned against ‘knee-jerk reactions’ to sex abuse claims.

‘As much as we hope some good will come of all these recent torrid retellings, there is also a danger that we are getting lost in the headlines and drama – knee-touching, bathrobes, swathes of sexual predators. It has now become a full-blown media maelstrom.