Eighteen years on from his time inside the Twelve Tribes religious sect, Matthew Klein is still scarred.

"They not only control your medical care, they control your food, when you get to see your family, they try to control when you make love to your wife, they try and control your children," he told A Current Affair .

"Once you've been there a while, you realise that not everyone is equal. There are leaders and there's a whole hierarchy within it. It's very similar to Animal Farm ."

Klein, his wife Tysha, and their two children joined the Twelve Tribes in 1999, drawn to their communal lifestyle and strong faith.

The Twelve Tribes present themselves as a welcoming religious group, growing produce on their New South Wales properties, and selling food through their cafes. For Klein, it felt like a simple way of life.

Matthew Klein, a former member of the Twelve Tribes church, has spoken out about some of the group's practices. (A Current Affair)

In the first six months within the Australian arm of the group, Tysha gave birth to another son. A few weeks later, their baby began having breathing difficulties. The elders discouraged them from seeking outside medical help.

This was not the only practice that concerned Klein.

According to Klein, the Twelve Tribes child training manuals provide detailed instructions about severe disciplinary measures for children, starting as young as six months old.

Concerns have been raised over the group's treatment of children. (A Current Affair)

"They would get spanked from morning and night," he said.

"They would get spanked 20 to 30 times a day. Each one of them is six strikes on the hand with a thin rod."

The Twelve Tribes was started by former high school teacher and carnival showman Eugene Spriggs in Chattanooga, Tennessee, in the 1970s. Spriggs created the Twelve Tribes as a loose hybrid of Judaism and Christianity, preaching to his followers to live by the "first testament".

Eugene Spriggs is the founder of the Twelve Tribes. (A Current Affair)

When members join, they're baptised with Hebrew names, hand their money and possessions, and live together in a commune.

The Australian arm of the tribe was formed in the early 90s, when Spriggs sent two Americans to set up the group in the Blue Mountains – Scott Sczarnecki and William Nunnally.

Today members live in one of their two Sydney bases: bedroom heritage house in Katoomba, and a 45-acre property just outside of Picton.

The Twelve Tribes present themselves as a harmless church, with much singing and dancing. (A Current Affair)

The group operates The Yellow Deli in Katoomba and The Common Ground Bakery in Picton.

"They don't pay wages, they don't pay superannuation, they don't pay insurances, they don't pay anything. They don't pay tax because apparently, they're a church. And where all this money goes, I don't know," says Klein.

Children in the Twelve Tribes are put to work from a very young age. Klein's now 23-year-old daughter Tessa remembers being sent out to work in a candle factory when she was five years old.

Matthew's daughter Tessa said she was put to work at five years old. (A Current Affair)

" Working with this boiling wax, like dipping into it making candles, like completely alone," she tells A Current Affair .

Rosemary Cruzado left the Twelve Tribes in 2010 after nearly 14 years.

"I was brainwashed the whole time I was there … like I was unable to critically think of anything."

The secretive group has a 45-acre property outside the NSW town of Picton. (A Current Affair)

Cruzado had two pregnancies during her time there. At 38 weeks during her last pregnancy, the baby stopped kicking and Rosemary experienced seizures.

The Australian leaders of the tribe did not want her to go to hospital. She recalls William Nunnally explicitly telling her "You can't end up in hospital."

Cruzado's baby died in utero, and the baby was taken away immediately.

Rosemary Cruzado left the Twelve Tribes after nearly 14 years. (A Current Affair)

"They laid it so thick on us on both my husband and I, they said it was all our fault that god couldn't really blessed us with a live baby because of our sin," she said.

While he was living within the Twelve Tribes, Matthew Klein convinced himself that the fanatical religious group was not a cult.

Once he got out, he quickly changed his mind. He's hoping by speaking out, he will prevent others from joining.

The Twelve Tribes sells food through its Yellow Deli cafes. (A Current Affair)

"I think it's my social duty to warn other people of what goes on in this place," he said.

"It's the kids who don't have a choice and it's just not on."