They are preparing an application to the fertility watchdog that would allow them to screen out male embryos to reduce significantly the chance of a couple having an autistic child.

As boys are four times more likely to be born with autism than girls, couples with a family history of the condition want to ensure they have only girls. Such sex selection is not at present permitted.

The technique, called pre-implantation genetic diagnosis (PGD), has been used to create babies free from life-threatening illnesses such as Duchenne muscular dystrophy and haemophilia.

However, screening embryos to prevent babies being born with autism would prove controversial because children born with the disorder can live long and healthy lives. Critics claim the treatment would be a step closer to creating babies free from all imperfections.

The team at University College Hospital’s assisted conception unit in London decided to apply for a licence for the procedure after they were approached by a couple with a history of autism in the family.

Joy Delhanty, professor of human genetics at University College London medical school, said couples would undergo the treatment only if autism had inflicted severe suffering on the family.

Couples requesting the procedure would need to go through a gruelling in-vitro fertilisation cycle, even though they had no difficulty conceiving naturally. The technique could be used only to prevent the hereditary form of autism, which affects about 10% of cases. It is not known what causes autism in many children.

Delhanty said: “Normally we would not consider this unless there were at least two boys affected in the immediate family. We would be reducing the risk of autism. Couples are not going to undertake this lightly when we explain what they are going to need to go through.”

Two other families have previously approached the clinic requesting pre-implantation genetic diagnosis. In both cases they are understood to have had two sons with autism and hoped to have a daughter free from the condition.

Delhanty hopes that now that the rules have been relaxed to allow PGD screening for breast cancer the authorities will also consider screening for autism. The team will research the pros and cons of the technique further before submitting an application to the Human Fertilisation and Embryology Authority.

The development would be strongly opposed by disabled groups. Simone Aspis, parliamentary and campaigns worker for the British Council of Disabled People, said: “Screening out autism would breed a fear that anyone who is different in any way will not be accepted. Screening for autism would create a society where only perfection is valued.”

• Tony Blair has called for a new debate on late abortions. At a private meeting he told Cardinal Keith O’Brien, head of the Catholic Church in Scotland, that most MPs might now back lowering the 24-week limit. He said there were “very troubling issues” involved and that the viability of foetuses had changed since the legislation was introduced in 1967.

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