Climate change is forcing Cambodian farmers off their lands and into the clutches of a predatory brickmaking industry where a lifetime of debt bondage awaits them and their children, according to a study released today.

Key points: The poorest, most indebted farmers are entering brickmaking as bonded labourers

The poorest, most indebted farmers are entering brickmaking as bonded labourers Many take their whole families, meaning child labour is endemic in the industry

Many take their whole families, meaning child labour is endemic in the industry Factory owners keep children or the elderly as "de facto hostages" when workers want to travel

Researchers from Royal Holloway at the University of London have for the first time drawn a clear link between climate change and modern slavery in Cambodia's brickmaking industry, where indebted former-farmers are putting their families' lives on the line to make so-called "blood bricks" that feed the country's construction boom.

"The impact of climate inducing [people] to migrate is something that we see across a lot of industries, but the debt bondage is something unique to the brick industry," researcher Laurie Parsons told the ABC.

Sorry, this video has expired Cambodian brick workers become virtual slaves (Supplied: Royal Holloway, University of London/Thomas Cristofoletti)

It's really striking, it's extremely widespread. It isn't something that just happens in some factories — it happens in every factory."

Cambodia is one of the countries most vulnerable to climate change, with unseasonable drought and unpredictable rainfall increasingly forcing farmers to search for jobs in cities.

Dr Parsons said that transplanting — a cost-effective, traditional farming method of moving rice between fields — relied on rain falling predictably during two peaks of the year, which used to occur with regularity.

Most Cambodian farmers primarily cultivate rice, a pursuit the researchers say has become precarious in part due to climate change. ( Supplied: Royal Holloway, University of London/Thomas Cristofoletti )

"Now the rainfall comes in one large lump and [even] less predictably within that, [so] it's necessary to do different kinds of farming that require a lot more money," he said.

"This means that every farmer risks not only not having a good crops, but of being bankrupt every time they farm."

Many, burdened by spiralling microfinance debt and hounded by loan sharks, are now turning as a last resort to brick factory owners, who buy up their debts and put them to work until they can pay off the money.

The only problem is, few people ever can or do pay off the loans.

One woman, who was identified only as Achariya in the report to protect her identity, said that she was told to take over her parents' debt when she reached adulthood.

"My debt keeps on increasing now that I have a husband and children," she said.

"In the future, my children will do the same, sign their thumbprints to take my place."

'It's a place where people go and don't come back'

Brick-moulding machines like this one present a serious danger of limb loss, but workers have little choice but to use them. ( Supplied: Royal Holloway, University of London/Thomas Cristofoletti )

"Brickmaking is very difficult and physically demanding work — it tends to be something the poorest people do," Dr Parsons said.

"It's very much a last resort.

"Nobody wants to work in the brick industry; everybody knows it's a place where people go and they don't come back."

Whole families work on the brick kilns — a dirty, low-paid, and physically dangerous job — to create construction materials for some of Phnom Penh's most luxurious developments.

Children that grow up in the brick factories can also end up taking on their parents' debt when they reach adulthood. ( Supplied: Royal Holloway, University of London/Thomas Cristofoletti )

And when they want to travel home for a special occasion — such as a wedding or a funeral — it's common for one family member to stay behind at the factory.

"In some cases you see family members being kept as de facto hostages, often a child or an elder member," he said.

"A few family members will be allowed to leave while the other ones are kept back, sometimes in the kiln owner's house."

It is commonplace for children to live in brick factories with their parents, who are often working to pay off thousands of dollars in debt. ( Supplied: Royal Holloway, University of London/Thomas Cristofoletti )

The new research estimates that tens of thousands of people across the country could be affected.

Dr Parsons' research team spent months talking to families who had entered the notorious industry, with many sharing harrowing tales of loss and hardship.

Many of the workers have lived most of their lives in the brick factories — and their children face a similar future. ( Supplied: Royal Holloway, University of London/Thomas Cristofoletti )

Cambodia has enacted legislation prohibiting the use of child labour and forced labour, and is also a signatory to relevant international laws.

But Dr Parsons said authorities did not enforce the laws in the brickmaking industry as it "isn't seen as a priority".

The ABC sought comment from the Government and contacted a spokesperson, but no comment was provided.

Amputated limbs and life-threatening illnesses

Brick kilns are notorious for the pollution they emit into the atmosphere, a situation that is worsened when they burn rags for fuel. ( Supplied: Royal Holloway, University of London/Thomas Cristofoletti )

Brickmaking — particularly using the rudimentary kilns most commonly employed in Cambodia — comes with major health risks including the possibility of amputated limbs from the dangerous machinery and life-threatening respiratory illnesses developed from noxious gases released into the atmosphere, which also contributes to environmental degradation.

"One of the things we see in brick kilns is that a lot of people simply drop dead at a relatively young age, in their 30s and 40s and 50s," Dr Parsons said.

"There was a woman who lost her husband to that kind of sudden death; she lost her brother and her child had an accident a couple of years ago where he fell underneath a stack of brick and broke his back.

"Just talking to her and seeing how she was able to cope and maintain dignity, that was something I found quite amazing."

And amid all this pain and suffering, Dr Parsons said, brick kiln owners generally don't think there's anything wrong with what they're doing.

In many rural villages, families are just one illness away from having to enter brick work due to unsustainable debt. ( Supplied: Royal Holloway, University of London/Thomas Cristofoletti )

As kiln owners buy the finished bricks on a piece-rate basis from workers, they believe they are removed from any responsibility for the production process.

"This is one of the reasons child labour is so endemic, because they don't buy the bricks from the child, they buy them from the head of the family, usually the father," Dr Parsons explained.

"And whether their wife is involved or their children are involved in making the bricks, that's not the brick kiln owner's problem, as far as they see it.

"They just provide the equipment."