Child labour is the practice where children engage in economic activity, on part or full-time basis. The practice deprives children of their childhood, and is harmful to their physical and mental development. Poverty, lack of good schools and growth of informal economy are considered as the important causes of child labour in India.  
The 2001 national census of India estimated the total number of child labour, aged 5–14, to be at 12.6 million.  Child labour problem is not unique to India; worldwide, about 217 million children work, many full-time. 
In 2001, out of a 12.6 million, about 12 million children in India were in a hazardous job.  UNICEF estimates that India with its larger population, has the highest number of labourers in the world under 14 years of age, while sub-saharan African countries have the highest percentage of children who are deployed as child labour.    International Labour Organization estimates that agriculture at 60 percent is the largest employer of child labour in India,  while United Nation 's Food and Agriculture Organization estimates 70 % of child labour is deployed in agriculture and related activities.  Outside of agriculture, child labour is observed in almost all informal sectors of the Indian economy.   
Companies including Gap,  Primark,  Monsanto  and others have been criticised for child labour in their products. The companies claim they have strict policies against selling products made by underage kids, but there are many links in a supply chain making it difficult to police them all.  In 2011, after three years of Primark 's effort, BBC acknowledged that its award-winning investigative journalism report of Indian child labor use by Primark was a fake. BBC apologized to Primark, to Indian suppliers and all its viewers.   
Article 24 of India 's constitution prohibits child labour. Additionally, various laws and the Indian Penal Code, such as the Juvenile Justice (care and protection) of Children Act-2000, and the Child Labour (Prohibition and Abolition) Act-1986 provide a basis in law to identify, prosecute and stop child labour in India. 
International Labour Organization (ILO) states that child labour may be defined in a number of different ways, and a different definition yields a different estimate of child labour in India as well as other countries. According to ILO, children or adolescents who participate in work that does not affect their health and personal development or interfere with their schooling, is not child labour; rather it may generally be regarded as being something positive. Such harmless work includes activities such as helping their parents around the home, assisting family or earning pocket money outside school hours and over holidays. These kinds of activities, suggests ILO, may contribute to children’s development by providing them with skills and experience, and help to prepare them to be productive members of society during their adult life.
The term child labour, suggests ILO is best defined as work that deprives children of their childhood, their potential and their dignity, and that is harmful to physical and mental development. It refers to work that is mentally, physically, socially or morally dangerous and harmful to children, or work whose schedule interferes with their ability to attend regular school, or work that affects in any manner their ability to focus during school or experience healthy childhood.
UNICEF defines child labour differently. A child, suggests UNICEF, is involved in child labour activities if between 5 to 11 years of age, he or she did at least one hour of economic activity or at least 28 hours of domestic work in a week, and in case of children between 12 to 14 years of age, he or she did at least 14 hours of economic activity or at least 42 hours of economic activity and domestic work per week. UNICEF in another report suggests, "Children’s work needs to be seen as happening along a continuum, with destructive or exploitative work at one end and beneficial work - promoting or enhancing children’s development without interfering with their schooling, recreation and rest - at the other. And between these two poles are vast areas of work that need not negatively affect a child’s development."
India 's Census 2001 office defines child labor as participation of a child less than 17 years of age in any economically productive activity with or without compensation, wages or profit. Such participation could be physical or mental or both. This work includes part-time help or unpaid work on the farm, family enterprise or in any other economic activity such as cultivation and milk production for sale or domestic consumption. Indian government classifies child laborers into two groups: Main workers are those who work 6 months or more per year. And marginal child workers are those who work at any time during the year but less than 6 months in a year.
Some child rights activists argue that child labour must include every child who is not in school because he or she is a hidden child worker. UNICEF, however, points out that India faces major shortages of schools, classrooms and teachers particularly in rural areas where 90 percent of child labour problem is observed. About 1 in 5 primary schools have just one teacher to teach students across all grades.