In June this year a thick haze descended over Singapore, causing record air pollution levels which left streets empty and forcing children, the sick and elderly to stay indoors. It was attributed to the illegal burning of forests in Indonesia to clear land to plant palm oil. It was a visible reminder of a practice which has been continuing for years but, say environmental groups, which must be stopped.

Palm oil is in hundreds of products, from detergents and cosmetics to biscuits and now biofuels. But the burning of forests is destroying the habitat of endangered wildlife, destroying woodland and releasing carbon dioxide from the peat. Tom Heap asks if we've turned a blind eye to this issue. Some manufacturers have pledged to source sustainably but he asks how sure they are the oil they get is untainted.

Costing the Earth heads to Indonesia to see the level of destruction, find out who's behind it and looks at the impact the haze has had on Singapore. In France politicians have called for a levy on palm oil and consumers have campaigned against it but is this an issue the British still want to know about?

Produced in Bristol by Anne-Marie Bullock.