In a 110-page report accompanied by a video, Amnesty alleged products sold by those companies were “tainted by appalling human rights abuses ... with children as young as eight working in hazardous conditions”.

It called on the companies implicated to tell customers whether the palm oil in individual products such as Magnum ice-creams, Ariel detergent, Knorr soup, Pantene shampoo and Aero chocolate bars were made using child labour.

“These findings will shock any consumer who thinks they are making ethical choices in the supermarket when they buy products that claim to use sustainable palm oil,” said the senior Amnesty investigator Meghna Abraham.

“There is nothing sustainable about palm oil that is produced using child labour and forced labour. Something is wrong when nine companies turning over a combined revenue of £260 billion (US$324 billion) in 2015 are unable to do anything about the atrocious treatment of palm oil workers earning a pittance.”

She said allegations of child labour at Wilmar were not “isolated incidents but are systemic and a predictable result of the way Wilmar does business”.

In the report, Amnesty alleged that children aged from eight to 14 were carrying out dangerous work without safety equipment, were exposed to toxic pesticides and regularly carried sacks of palm fruit weighing 25kg.

One 10-year-old boy, who claims he started working for a Wilmar supplier aged eight, said he gets up at 6am to gather fruit and works every day but Sunday. “I don’t go to school ... I carry the sacks with the loose fruit by myself but can only carry it half full. My hands hurt and my body aches,” he said.

When approached by Amnesty, seven of nine companies admitted that they use palm oil from Wilmar’s Indonesian supply network but only two – Kellogg’s and Reckitt Benckiser – offered any detail about which products were affected.

The two companies cited “traceability” as a factor in why they had not been aware of abuses at the plantations supplying them palm oil through Wilmar.

“Using mealy mouthed excuses about ‘traceability’ is a total cop-out from those companies,” said Amnesty’s business and human rights programme director, Peter Frankental.

“You can be sure that if one of these companies’ products were contaminated and had to be taken off the shelves of supermarkets, they would ensure that they could trace the source to specific plantations.”

Wilmar said it was aware of allegations about labour rights abuses before it was contacted by Amnesty and was already taking steps to remedy any failings.

“Wilmar has put a lot of effort and systems in place to deal with labour and social issues in our operations and supply chain,” the company said. “We acknowledge that there are ongoing labour issues in the palm oil industry, and these issues could affect any palm company operating in Indonesia.

“The focus on Wilmar, as the largest processor and merchandiser of palm and lauric oils worldwide, is often used to draw attention to problems in the wider palm oil industry.”

Colgate-Palmolive said: “We are concerned about the specific allegations raised by Amnesty International and will hold Wilmar accountable for addressing any issues.” It said it would “terminate any supplier that fails to address labour and human rights concerns”.

A Nestlé spokesperson said: “We will investigate allegations related to our purchasing of palm oil, along with our suppliers.” The company said it was not currently able to trace its products back to the plantations in Amnesty’s report.

Kellogg’s said: “If we find ... any supply chain violations of our global palm oil principles, we work with the supplier to understand corrective actions and ensure they understand our commitments. If the concerns are not adequately addressed, we take action to remove them from our supply chain.”

Another company, Procter and Gamble, said it had been “working with Wilmar to ensure they can remedy any potential human rights infringements in their supply chain”.