Scientists have discovered a poppy that does not produce addictive drugs - and are using it to make safer painkillers.

Poppies are used to make the pharmaceuticals morphine and codeine, which act as painkillers but are also the raw ingredients for illicit drugs such as heroin and opium.

Philip Larkin, of Australia's Commonwealth Scientific and Industrial Research Organisation, and colleagues describe a mutant poppy that produces neither of these addictive chemicals in today's Nature.

The biochemical pathways normally present in poppies that produce these chemicals are blocked in the naturally occurring mutant, known as top1.

This leads the plant to accumulate related chemicals, thebaine and oripavine, which can be extracted and made into non-addictive painkillers.

Dr Larkin said painkillers such as buprenorphine were inherently safer because they limit their own activity in the brain at high doses - in other words, it is hard to overdose on them.

In Tasmania the mutant is being used to produce around half of the poppy crop.