Deep in the jungle of Jharkhand state in eastern India, at the end of a rutted track passable only by motorbike, a six-year-old girl named Sonia sat in the scorching midday sun, sifting jagged stones in an open-cast mine in the hope of earning enough money for a meal.

Sonia was halfway through her working day and she was already exhausted and dishevelled. Her hair was matted and her pretty flower-patterned dress spoilt by dust.

She barely had enough energy to glance at her eight-year-old cousin Guri, toiling intently beside her as they searched the stones for pieces of mica, a shiny material whose many uses include putting the sparkle into make-up.

If the girls spotted enough mica, they might earn 63p each for a 12-hour day. If they found none, they would probably go hungry.

The contrast between this ugly scene of exploitation, hidden from view in a forest teeming with Maoist guerrillas where few westerners dare to venture, and the glamour of the cosmetics industry could hardly be more glaring.

India’s exports of mica are used to make paints and electronic goods as well as glossy lipstick and eyeshadow. Campaigners against child labour believe cosmetics manufacturers sensitive to the views of consumers could do most to bring about reform.

“It is most disturbing that six-year-old girls are involved in mines to beautify ladies all over the world,” said Bhuwan Ribhu, from the child rights group Bachpan Bachao Andolan (BBA). “More action needs to be taken by cosmetics companies, consumers and governments.”

It was this organisation, accompanied by The Sunday Times, that found Sonia with at least 15 other children scrabbling in the dirt of one of the forgotten corners of India, about 700 miles east of the capital, New Delhi.

They were by no means the only ones hard at work in the mine while their more fortunate contemporaries laboured over English and maths books in the few local schools.

Sita Dave, an impoverished mother, was there with her five sons, aged seven to 15, all dressed in school uniforms but sifting stones like the rest.

“If we each earn 50 rupees (63p) in a day then we eat,” she said simply. “Sometimes we don’t.”

Within a few hours, two other groups of small children were found working in separate places. Santu, 12, said he was earning money because he had no mother and his father was suffering from tuberculosis.

Times Recommends

• 'New York has lost its edge'
• Copenhagen will fail – and quite right too
• More than 17,000 new underwater species found