“Invisible hands” depicts children working in modern slavery in cacao plantations in Ghana, accessory factories in India and tobacco farms in the United States.

“They are not hidden at all,” director Shraysi Tandon told the Thomson Reuters Foundation by phone ahead of the film’s premiere in New York on Friday.

She said major firms were showing “willful ignorance” over child labor in their supply chains because they see it as too much cost and effort to tackle the problem.

More than 150 million children were working globally in 2017, according to a report from the International Labor Organization, with the UN saying climate disasters and conflict had pushed millions into child labor.

Tandon said the average age of child labourers she spoke to while making the film was 12, but the youngest was a girl of four or five working on a tobacco plant in Indonesia.

“She was tying the tobacco leaves to the stick and she was so little that just lifting one or two tobacco leaves was difficult for her,” she said.

The effects on child labourers were often lifelong, she said, as they were exposed to dangerous chemical and heavy machinery while the lack of an education also left them trapped in menial work.

“They are extremely vulnerable and susceptible to all forms of exploitation,” she said.

In many cases children are exposed to worse conditions than adults, she said, because to provide safety equipment in their size would amount to a tacit acknowledgement of their existence in the workforce.

Some are also trafficked, with many suffering sexual abuse from the adults who control them.

“If the kids do some good work they are sexually assaulted and that’s their ‘reward’ and if they mess up they are also beaten, punished and sexually assaulted,” she said.

Meanwhile, major brands are failing to make sufficient efforts to root out child labor and trafficking from their often-complex supply chains because they see it as too difficult and expensive to take on, Tandon argued.

“They are competing in the global market, and if you want to keep costs low and profits high you tend to avoid those things,” she said.

She called for firms to map and audit their suppliers and for consumers to research whether slave labor is likely to have gone into the products they buy and lobby for change.

“Companies take action when their brand or reputation is being threatened,” she said.