Would-be reality star with four wives and 16 children sparks row over polygamy

When the advertising salesman Kody Brown, his wife Meri, and his three other wives, Janelle, Christine and Robyn, decided to invite a film crew into the home they share with no less than 16 children, they presumed that a life of reality TV stardom would beckon.

Instead, the family has found itself at the centre of a snowballing public debate after police in Utah responded to Sunday's premiere of Sister Wives by launching an investigation into the polygamous lifestyle that Brown and his spouses have chosen to pursue.

Prosecutors in Lehi, south of Salt Lake City, announced that they believe the Browns are guilty of not just violating state laws against plural marriage, but of celebrating the crime in front of millions of television viewers.

In Sister Wives, the Browns try to expose what they call the benign truth about how a plural marriage works. "We're a very integrated family," argues Kody. The opening episode introduced viewers to his wives Meri, Janelle and Christine, before showing how they go through the occasionally traumatic process of adding a fourth wife, Robyn, to their already sprawling household.

"I think we're normal," says Christine, of their domestic arrangement, in which the wives take turns to sleep with Kody. "People ask, 'How do you feel when he's off with another woman, having sex?' I say 'Gosh, darn it, he better!'"

The show has shed light on the modern face of polygamy – a practice originally endorsed by the 19th-century founders of the Mormon Church. Plural marriage was made illegal, as a condition of Utah joining the US in 1896. But although today's Mormon Church excommunicates polygamists, polygamy is still practised by an estimated 40,000 families in Utah.

Most modern polygamists call themselves fundamentalist Mormons, and only legally register the first of their many marriages. Many also live prosperous existences and are considered respectable, if somewhat eccentric, members of society.

But that is no defence to felony bigamy, the crime that the Browns are being investigated for: under the state's laws, a person can be found guilty of bigamy through mere co-habitation. In 2001, a Utah man called Tom Green, who had brought his five wives on TV chat shows, was convicted of bigamy.

Since then, local police have endorsed a policy of live and let live, choosing only to investigate polygamist families in which other offences such as incest, violence, and child rape are believed to have been committed.

Kody Brown and his wives are not suspected of any such crime, however. "The closest analogy to the Browns is Hugh Hefner," said Paul Murphy, at the Utah Attorney General's office. "Here is a man who has three women. Do we want to spend state resources prosecuting these people and putting the kids in foster care?"

For now, the Browns say the investigation, while "disappointing", is a price worth paying for increasing public understanding of their lifestyle.