An investigation of child labour around the world has revealed that 76 countries represent "extreme" risks of complicity in child exploitation for companies.

The Child Labour Index, published by the risk analysis firm Maplecroft, concludes that worsening global security and the economic downturn have led to an increase in child labour over the last year.

Authoritarian countries or those in the grip of conflict are most prone to the exploitation of children, says the report. Burma, North Korea, Somalia and Sudan are ranked as the joint worst offending nations.

The Democratic Republic of Congo, Zimbabwe, Afghanistan, Burundi, Pakistan and Ethiopia also featured in the top 10 extreme-risk nations.

Some of the largest growth economies, such as the Philippines, India and China, are classed as an extreme risk and pose a serious concern for companies aiming to avoid child labour in their international supply chains.

The problem is found across industries. In India, evidence of child labour has been found in factories, gemstone cutting, quarrying, brick kilns, silk thread production and textile embroidery.

International Labour Organisation (ILO) figures count 215 million children working across the world - 115 million of them in hazardous jobs. Some 150 million are thought to be under the age of 14.

"Business can be directly implicated or can be deemed complicit in violations of the prohibition of child labour if children are found to be working within their operations or are used by their suppliers in circumvention of relevant ILO standards," said human rights analyst Chris Kip.

"Companies should ensure stringent human rights due diligence within their supply chain is undertaken to reduce the risk of damaged reputations, litigation, investor alienation and consumer backlash."

Professor Alyson Warhust, CEO of Maplecroft, said child labour required a "responsible solution".

"It is not just a question of eliminating children from the workforce, but checking on the impacts of doing so, as children need help to get back into education, if schools exist, and families may depend on the income from child labour, pushing children into precarious working condition," she added