Dressed in her sharp pinstripe suit, her dark brown hair elegantly coiffed, Vicky looks every inch the archetypal young working woman after a day at the office. But there are things she does not talk about at work.

Things such as the house she grew up in with her 39 brothers and sisters. Things such as the 21 children, six of them her own, who run around the house she lives in now. Things such as the two other “sisterwives,” one of them her blood sister, with whom she she shares her husband, taking turns to spend the night with him in strict rotation. “It’s not a thing we generally publicise,” she says shyly.

Now, however, Vicky is going public, although she declines to use her last name. As high-profile cases of child sex abuse among secretive cults unsettle and anger the larger polygamist community, women like Vicky are stepping forward to lobby in defence of a woman’s right to be a plural wife without fear of prosecution. “We live good and decent lives,” she said.

Going public on polygamy has long been a risky business in Utah, where an estimated 40,000 polygamists live below the legal radar. For the past 50 years Utah has had a strict “don’t ask, don’t tell” policy towards the practice, a felony punishable by up to five years in jail. The policy was prompted by a raid in 1953 on a polygamist community that ended with hundreds of children taken into care and parents jailed, causing a public relations disaster.

Some groups retreated into compounds. Those living among the wider community kept their mouths shut and their heads down. Parents avoided taking their children to the dentist or doctor, fearing the discovery of their secret. Children were warned not to bring friends home from school – if they were allowed to go.

Murmurs persisted of dark acts among some of the many splinter groups of Mormon fundamentalists, the umbrella term for those who broke away from the main Church of Jesus Christ of Latter-Day Saints over the practice 100 years ago.

Then in 2003, in a direct challenge to prosecutors, Tom Green, a polygamist, began appearing on television shows to argue his right to his five wives.

“I’d never really thought about prosecuting polygamy,” said Mark Shurtleff, a mainstream Mormon who had been elected Utah attorney general the year before. “But it’s a felony and he’s out there flaunting it.” Investigators discovered worse: Mr Green’s youngest bride was only 13 and had borne him a child – proof of a sexual relationship. Mr Green was charged with child rape and polygamy.

The case opened up a Pandora’s box for Mr Shurtleff. Emboldened, escapees from the Fundamentalist Church of Jesus Christ of Latter-Day Saints, the closed cult led by Warren Jeffs, came to tell their stories. “The stories were horrendous,” he said. Carolyn Jessop, who escaped with her eight children, told him of forced child marriages, the abuse of young boys and girls and threats to slit their throats if they left.

“Here’s what I had to decide,” Mr Shurtleff explains. “We had to do something. How are we supposed to prosecute all the polygamists, 20,000 people? It can’t be done. So we decided ‘We’ll go after child rape, child sexual assault. We’ll make it about that, not religion’.”

A warrant was issued for Mr Jeffs’s arrest on charges of aiding child rape instead of polygamy. He went on the run but was recaptured in August. The shocking testimony of a former child bride at a hearing earlier this month convinced a judge to send Mr Jeffs to trial. The hearing is set to begin in April. The stories of Mr Jeffs’s church horrified many other polygamists who regarded his actions as an abuse of God’s law. To them polygamy is a religious duty that they must undertake to reach the highest level of heaven.

Anne Wilde, the widow of a high-profile polygamist, decided it was time to save the reputation of the community as a whole. She began collecting the oral histories of plural wives to publish in a book and created a website for her organisation, Principle Voices. She launched a pro-polygamy magazine, Mormon Focus, and recruited Vicky to pose with her two sisterwives and their babies for the inaugural cover, taking lessons from same-sex marriage advocates to argue their right to an “alternative lifestyle”.

“It was also easier for me because I was no longer a plural wife,” Ms Wilde explains. “For those others, it was a brave thing to do.”

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