Human rights organisation Amnesty has accused Apple, Samsung and Sony, among others, of failing to do basic checks to ensure minerals used in their products are not mined by children.

In a report into cobalt mining in the Democratic Republic of the Congo, it found children as young as seven working in dangerous conditions.

Cobalt is a a vital component of lithium-ion batteries.

The firms said that they had a zero tolerance policy towards child labour.

The DRC produces at least 50% of the world's cobalt. Miners working in the area face long-term health problems and the risk of fatal accidents, according to Amnesty.

It claimed that at least 80 miners had died underground in southern DRC between September 2014 and December 2015.

It also collected the testimonies of children who allegedly work in the mines.

Paul, a 14-year-old orphan, started mining when he was 12 and told researchers: "I would spend 24 hours down in the tunnels. I arrived in the morning and would leave the following morning ... I had to relieve myself down in the tunnels … My foster mother planned to send me to school, but my foster father was against it, he exploited me by making me work in the mine."

UNICEF estimates that there are approximately 40,000 children working in mines across southern DRC.

In response to the report, Apple said: "Underage labour is never tolerated in our supply chain and we are proud to have led the industry in pioneering new safeguards."

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