By Dino Mahtani in Lagos

A US-based labour rights group has filed a lawsuit against three big food companies after an industry pledge to establish a certification system to help eradicate child labour on West African cocoa farms passed its deadline.

The International Labour Rights Fund (ILRF) filed the suit against Nestlé, Archer Daniels Midland and privately held Cargill last month, on behalf of three Malian children who were allegedly

trafficked to work on plantations in Ivory Coast, beaten and forced into hard labour. The preliminary hearing is expected to begin next Monday.

Chocolate and cocoa industry representatives signed an agreement in 2001 to develop a voluntary, industry-wide standard of public certification" by July 1 to help get rid of the worst forms of child

labour.

The agreement became known as the Harkin-Engel protocol after the US senator and congressman Tom Harkin and Eliot Engel who helped draft the document.

The move was seen as an attempt by industry to deflect harsher legislation in the light of media reports of slavery on cocoa farms in West Africa and the controversial case in 2001 of the MV Etireno, a Nigerian-registered ship believed to have trafficked children along the West

African coast. West Africa is the source of two-thirds of the $4.5bn (€3.6bn, £2.5bn) world cocoa market.

The International Labour Organisation (ILO) has said 284,000 children are employed in Ivory Coast, Ghana, Nigeria and Cameroon, according to a 2002 survey.

The case is the second filed by the ILRF to put pressure on the industry. Last year it filed a case against US customs at the US Court of International Trade evoking the US-Tariff Act, which prohibits the import of goods made through forced child labour.

In February this year the Chocolate Manufacturers' Association chose to intervene in the case as defendants, the ILRF said.

Additional reporting by Andy Bounds in Brussels