Two of Australia's most well-known football brands, Sherrin and Canterbury, have operations in India that use banned child labour.

A 12-month investigation by the Herald has discovered that despite significant reforms to India's massive but poorly regulated sports ball industry, children are still working, sometimes forced, in the painstaking and painful hand-stitching of footballs, netballs and soccer balls.

The children who stitch Sherrin and Canterbury balls are employed unofficially, through subcontractors, who pay them for each ball stitched.

Stitching together the four pre-cut panels of a Sherrin Auskick football can take more than an hour. To a stitcher, it is worth 7 rupees, about 12¢. A Canterbury rugby ball earns 11 rupees.

Soccer balls or netballs, with more panels, pay up to 28 rupees a piece, about 49¢, for three or four hours work, while the cheapest, smallest, footballs pay as little as 4 rupees.

Most child-stitchers earn about between 50 and 60 rupees, about a dollar a day.

The sourcing manager for Canterbury Australia and New Zealand, Jason Law, said he was "horrified" and "extremely disappointed" by the Herald's evidence.

"We will definitely be delving into it ourselves a lot deeper and making sure we stamp out whatever is going on up there."

The Australian managing director of Sherrin's parent company, Russell Corporation, Chris Lambert, said the use of child labour "in no way comes anywhere close to our standards of corporate social responsibility".

"It's not acceptable, and it's illegal. We are jumping on it straight away."

The children the Herald discovered stitching, sit, hunched on low stools, for between five and eight hours a day, six or seven days a week.

Stitchers often end up with chronic back injuries from the unnatural sitting position.

They regularly pierce their fingers with the sharp, heavy needles, or slice their hands on the wax-coated string.

Working inside and in the dark, as most child labourers do to keep them hidden from authorities, strains child stitchers' eyes and leads to vision disorders.

Keeping children from school to make them work is illegal in India. In 2010, the Right to Education Act made it compulsory for children under 14 to attend school.

India's child-labour laws lag behind, but legislation approved by cabinet last month and soon to go before parliament will prohibit the employment of anyone under 14.

Across Punjab's industrial cities, the Herald discovered children, almost all of them girls, and as young as seven, who have been pulled out of school to work in secret, stitching sports-balls full-time.

Sunali, 11, sits in her family's one-room home in Basti Danishmandan, Jalandhar, stitching Sherrin Auskick footballs with her sister Rupa, 10, and mother Laxmi. Together, they stitch 15 balls a day, for 105 rupees, $1.86 Australian.

Sunali used to go to school but doesn't any more. Instead she stitches six days a week. Her family needs the money.

"It is difficult [to keep them at home], but to eat, to feed my family, I have no choice,'' Laxmi says. ''We have to do this."

A subcontractor in the neighbourhood, Rajkumar, confirms the balls are from the factory of Sherrin's contractor Spartan, and will be exported to Australia.

In neighbouring Basti Pirdad, 12-year-old Reena goes to school infrequently. She has fallen three years behind her classmates.

The Herald finds her at home on a school day, sewing a Canterbury rugby ball.

Reena works at least five hours, seven days a week. "We are very poor people," her mother explains.

"Sometimes she is at school, but even if she goes, she comes home around 1pm and starts stitching. She stitches until it is dark."

India is the largest exporter of sports balls to Australia. Nearly 10 million Indian-made balls were shipped into the country last year, 45 per cent of all sports ball imports.

Both Canterbury and Russell Corporation have supply agreements with Indian sports ball manufacturers. Those manufacturers sign codes of conduct which outlaw child labour, and are regularly independently audited to ensure those conditions are met.

Presented with the Herald's findings, both Canterbury and Russell promised investigations.