"A huge amount still remains to be done to protect children's rights all over the globe and to prevent their exploitation," Unicef UK's executive director David Bull said.
From unregulated chemical plants in Asia to the giant open cast mines of Latin America and the stone quarries of West Africa, child labour is a scar on the conscience of the world in the 21st century, the report said. Children are forced to work not only as soldiers in African wars or in the sweatshops of Asia, but also as cheap farm labour in north America and prostitutes in Europe, it said.
"Estimates of the number of young people working on farms in the US vary from 300,000 to 800,000," the report said. "Many are from minority groups, particularly Spanish-speaking immigrant families."
It also cited prostitutes as young as 15 working on the streets of English cities. The report said children were born, sold or trafficked into what amounts to domestic slavery in many countries, some earning barely $1 a month.
The incidence of child labour is highest in Africa where 41 percent of those aged 5 to 14 are known to work, compared with 21 percent in Asia and 17 percent in Latin America and the Caribbean.
But Asia accounts for 60 percent of the world's working children because of its higher population.
Unicef stressed that not all working children were at risk, but noted that if school-age children were at work they were missing the education needed to lift them out of poverty and drudgery.
It said the only way to end child labour was to end poverty, and called on the rich industrialised nations to boost aid by $50 billion a year and meet a decades-old pledge to raise annual aid budgets to 0.7 percent of national income. Aid should be better targeted to help the poor directly and support should be given to help developing nations take charge of their own budgets and development programmes.
"2005 holds unprecedented opportunities for the UK government to use the G8 summit and its presidency of the EU to drive forward the fight against poverty, debt and trade injustices," Bull said. "It is a great opportunity to transform children's lives."