Researchers have found a way of reducing gossypol, a powerful toxin in the seeds, to a negligible level that allows them to be consumed by humans. At present they are thrown away or fed to cows.

Dr Keerti Rathore, a plant technologist at Texas Agricultural Experiment Station, which carried out the research, said enough cotton was already planted worldwide to supply the protein needs of 500m people.

“The exciting finding is that we have been able to reduce gossypol to a level that is considered safe for human consumption,” said Rathore, whose findings will appear in the Proceedings of the National Academy of Sciences.

Further field and safety trials are needed but if successful the technique could turn out to be the “killer application” that supporters of GM technology have long hoped for. They believe environmentalists would find it hard to object to a crop with the potential to reduce world hunger on such a scale.

Gossypol is not just toxic but is also a powerful natural male contraceptive. The sperm of men who eat foods containing gossypol become deactivated.

Cotton plants secrete the toxin into their stems, leaves and seeds because it affects pests in the same way, inhibiting their breeding and reducing their numbers.

Rathore and his colleagues got round this problem using a relatively new technique known as RNA interference, or RNAi, to suppress one of the key genes involved in producing gossypol. “Very few people realise that for every pound of cotton fibre the plant produces 1.6lb of seed,” said Rathore.

“Overall, the world produces 44m tons of cottonseed each year containing about 22% high-quality protein.”

Scientists have created cotton plants without gossypol before, through conventional breeding techniques,

but they were attacked by pests. Rathore’s method strips gossypol from the seeds only, leaving the rest of the plant protected.

For farmers there will be a potential surge in the value of a crop that can be sold for food as well as clothing. Environmentalists, however, remain sceptical. They point to similar claims made for crops such as golden rice, which was genetically engineered to contain vitamin A. It subsequently emerged that people would need to eat huge amounts to gain any benefit.

Sue Mayer, the director of GeneWatch UK, urged caution. “Poverty and hunger are complex problems caused by bad government, poor economies and war,” she said. “It is not just a matter of finding a new wonder plant.”

Explore UK News

• Crime News

• Education News

• Health News

• Science News

• Scotland News

Times Recommends

• Anne Darwin's performance of a lifetime
• Renaissance for canals as new boaters come aboard
• Case study: forced to marry a cousin at 17