If child labour was to stop, he said, the companies would have to pay considerably more to the farmers who grow cocoa.
Chocolate companies have been told they will have to pay more for cocoa if child slavery is to end in West Africa.
In an uncompromising message, Ivory Coast - the world's biggest producer of cocoa - has blamed the multinationals for keeping prices low and farmers in poverty, driving some of them into using forced labour.
Senior Ivory Coast ministers are pressing their case to the UK Government at meetings on Friday, and the chocolate companies have been called to the Foreign Office to explain their policies.
The Ivory Coast Prime Minister, Pascal Affi N'Guessan, said chocolate companies were only interested in their own profits.
If child labour was to stop, he said, the companies would have to pay considerably more to the farmers who grow cocoa.
The international industry itself was at the heart of the problem of child trafficking in Africa, he said, adding that multinationals had encouraged more and more developing countries to grow cocoa, which had forced down the price.
He named a price almost 10 times higher than it is now to ensure the quality of life for the seven million farmers and their families in Ivory Coast.
Two Ivory Coast cabinet ministers have flown to London for a meeting with the Foreign Office Minister for Africa, Brian Wilson.
After that, Mr Wilson will be seeing chocolate executives to try to persuade them to do more to ensure their products are not tainted by slave labour.
The industry says the buying chain for cocoa is so complex that it is impossible to guarantee the working practices on every farm.