GM mosquitoes created by a British laboratory and released in Cayman as part of an experiment could thrive in the wild to pose a risk to human health and the environment, it has been claimed.

The warning comes from GM critics and is based on the release of details from a study commissioned by the company involved, Oxitec.

The Oxford-based firm has dismissed the claims as ‘scaremongering’. However they will alarm the public and raise serious questions about the future of the technology.

The firm has developed a technique to genetically modify a range of insects with the aim of protecting human health and boosting food crop yields.

Generally, this involves inserting a lethal gene into males of the insects, which are released to mate with females in the wild with the result that any offspring die.

Oxitec has developed a GM mosquito which is designed to reduce the wild population in areas where they are responsible for passing on dengue fever to humans.

Experimental releases have already taken place in the Cayman Islands, Malaysia and Brazil, while there are plans to repeat this in the holiday hot spot of the Florida Keys and Singapore.

Oxitec has always argued that the male GM insects will routinely die a short period after being released and mating in the wild, so having no long-term impact. However, this has been challenged by Friends of the Earth, GeneWatch UK and the Third World Network organisation.

They say the evidence of the company’s own research, some of which was released under the Freedom of Information Act, questions this assurance.

The GM mosquitoes are created in such a way that they require the presence of the common antibiotic tetracycline to be born in the laboratory and thrive.

Oxitec argues that once they are released into the environment they no longer have access to tetracycline and therefore, after a short period, will die.

However, the company’s study reveals that 15per cent of GM mosquitoes survived for some time after release through inadvertent access to low levels of tetracycline.

In a joint statement, FoE, GeneWatch UK and the Third World Network, warned: “Biting GM females might cause unknown impacts on human health, such as allergies.

“The ecological implications of GM mosquitoes surviving and breeding are also unknown.”

Eric Hoffman of FoE America said: ‘Trials of its mosquitoes must not move forward in the absence of comprehensive and impartial reviews of the environmental, human health and ethical risks.’

Director of GeneWatch UK, Helen Wallace, said: “It is impossible to assess health or environmental risks if important information is concealed from public scrutiny.

“This confidential document reveals a fundamental flaw in Oxitec’s technology which should have halted their experiments.”

Oxitec has plans to release GM moths into British fields in a bid to curb a population that is responsible for attacking cabbages and other crops.

It says these tests, which may involve open release, could take place later this year. However, any such plan would have to be approved by the food and farming department, DEFRA.

The chief executive of Oxitec, Hadyn Parry, denied any attempt to keep people in the dark.

“This is poor quality scaremongering by FoE and GeneWatch and it is a pity they made no attempt to contact us before putting this material out in an attempt to confuse the public,’ he said.

“in all countries there is a regulatory system where experts examine whether or not there is significant  risk to human health or the environment. If there is, then no release can take place.”