Releasing genetically-engineered fruit flies in the wild could be a cheap alternative to pesticides, according to researchers.

A new study found that releasing the modified flies in an attempt to increase the male population could be an effective and environmentally friendly way to control pests.

Scientists at the University of East Anglia (UEA) and Oxford Insect Technologies (Oxitec) said releasing the flies to encourage non-viable matings could be used as an effective way of suppressing populations - saving crops around the world.

The Mediterranean fruit fly is a serious agricultural pest which causes extensive damage to crops and is c urrently controlled by a combination of insecticides, baited traps, biological control.

Lead researcher Philip Leftwich said the Mediterranean fruit fly infests more than 300 types of cultivated and wild fruits, vegetables and nuts.

Of all of the current techniques used to control these flies, the Sterile Insect Technique (SIT) is the most environmentally friendly, Dr Leftwich said.

He added: "The down side is that these males don't tend to mate as well in the wild because the irradiation method used for sterilisation weakens them.

"The genetically engineered flies are not sterile, but they are only capable of producing male offspring after mating with local pest females - which rapidly reduces the number of crop-damaging females in the population.

"Using this method means that the males do not have to be sterilised by radiation before release, and we have shown they are healthier than the flies traditionally used for SIT."

Researchers simulated a wild environment within secure eight-metre greenhouses containing lemon trees at the University of Crete.

When the modified flies were released, there was a rapid population collapse.