The Stop the Traffik coalition of campaigners against human trafficking have welcomed the announcement from Cadbury's this week that its Dairy Milk chocolate bars are to go Fairtrade.

Cadbury's Dairy Milk, the chocolate brand's best known product, is to receive Fairtrade certification by late summer.

Stop the Traffik praised Cadbury for the decision, which comes two years into its Chocolate Campaign to see chocolate manufacturers to use only ethically produced cocoa. The coalition's founder, Steve Chalke, is calling on other chocolate manufacturers to follow Cadbury's example.

"This is a very significant step in our campaign. We congratulate Cadburys on their commitment to justice and now look to their policy being adopted across their entire product range as well as to their lead being followed by other manufacturers.

"But the Stop the Traffik Chocolate Campaign marches on. We now call on Mars and other manufacturers to follow Cadbury’s lead and abandon their reliance on the use of cocoa produced through trafficked and exploitative forms of child labour," he said.

Stop the Traffik warns thousands of children are being trafficked onto cocoa plantations in the Ivory Coast and across West Africa to harvest the cocoa that makes the world's chocolate. The industry committed in 2001 to removing all forms of exploitative child labour from the chocolate supply chain, but Stop the Traffik says little progress has been made.

Stop the Traffik CEO Ruth Dearnley said the turnaround in Cadbury's stance demonstrated the strength of the consumer.

"This decision demonstrates the power of ordinary consumers to bring about change and freedom. Two years ago, when Stop the Traffik met with Cadbury we were told that the decision we have witnessed today was impossible and impracticable. This is a victory for every person who has complained, campaigned and spread the message," she said.

"But most of all it is a victory for every child held in exploitative labour on the cocoa farms of West Africa. However, let us not snatch defeat from the jaws of victory - they will not be set free until Mars and Nestle and Lindt and Hershey and all the others have the integrity to put human rights before profit and make similar announcements."