Three quarters of women among India's Dawoodi Bohra sect have undergone female genital mutilation (FGM), according to a study published on Monday which comes just weeks after government officials said there was no data to support its existence.
Campaigners hope the survey - the largest of its kind - will bolster calls for a law to ban the secretive ritual which they say causes physical, emotional and sexual harm.
One mother told how she feared her daughter would bleed to death after she was cut. A third of women believed the procedure had damaged their sex lives. Others spoke of emotional trauma.
Traditional circumcisers told researchers they had cut thousands of girls.
Masooma Ranalvi, founder of campaign group WeSpeakOut which commissioned the study, said the stories were "heartwrenching."
"This report not only proves FGM does exist in India, but also shows how harmful it is," Ranalvi told the Thomson Reuters Foundation. "Children are still being cut today. This must end."
The year-long study - published on the eve of International Day of Zero Tolerance for FGM - includes 94 interviews with supporters and opponents of the practice.
The Dawoodi Bohra, a Shia Muslim sect thought to number up to 2 million worldwide, considers the ritual, known as khafd, a religious obligation although it is not mentioned in the Quran.
The procedure, which entails cutting the clitoral hood, is performed around the age of seven.
India's Supreme Court is considering a petition to ban FGM. Campaigners were shocked in December when the women's ministry told the court there was no official data or study supporting its existence.
FGM is more commonly linked to a swathe of African countries where cutters may remove all external genitalia.
Supporters of khafd say it is just a nick and cannot be classed as FGM. But the World Health Organization says FGM includes any injury to the genitalia.
One gynaecologist told researchers it would be easy to damage the clitoris if a girl struggled during the procedure which is done without anaesthesia.
Ranalvi said khafd was rooted in beliefs a woman's sexual desire must be curbed, but it was "mired in secrecy" and few women dared speak out for fear of ostracisation.
The practice made headlines in 2015 when three members of the Bohra diaspora in Australia were convicted of FGM-related offences. Bohras in the United States face similar charges.
Respondents to the survey said Bohra girls from diaspora communities were now travelling to India to be cut.