"Tin mining companies and independent smelters should refuse to buy any tin ore clearly or strongly allegedly supplied by illegal mining activities," the statement said.

"It is hoped that the whole tin industry supports these aims and buys only from legitimate sources," it added. The statement was released via Wildshaw, the global commercial representative of Peru-based Minsur, the world's second largest tin producer. The producers, who had gathered in London last week during the annual Dinner Week of the London Metal Exchange (LME), said they were worried about illegal mining on Bangka and Belitung islands in Indonesia.

The two islands are responsible for 85 percent of the tin produced by PT Timah , the world's largest integrated tin producer, which is 65 percent government-owned.

According to Erry Riyana Hardjapamekas, President Director of PT Timah who made a presentation to representatives of the other producers, the number of illegal miners on Bangka had spiralled over the past six months and stood at about 30,000. Much of the illegal tin ore coming from Bangka, where production costs are much lower than those paid by Timah, is believed to be shipped to neighbouring Singapore before being sold to Malaysian and Thai smelters.

Mining safety was another key issue, the five producers said, citing recent accidents in China, where illegal tin mining has become rampant.

Last month China's southwestern Guangxi region launched a campaign to shut down scores of illegal mines dug haphazardly by private firms after 80 people died in an accident in July.

"All tin mining companies should observe the highest environmental and safety standards, both during mining operations and after they have ceased to properly rehabilitate the areas mined and return them to their natural state," the statement said.