LESBIAN families and single women could overtake heterosexual couples as the largest group having donor insemination treatment at infertility clinics, according to experts.

Official figures show that the proportion of such women seeking treatment has increased from 18% in 1999 to 38% last year – evidence, say sociologists, of the growing acceptance by society of women-only families.

They are now to be recognised as “co-parents” on birth certificates in a development that is expected to be enshrined in new legislation next year.

The new Human Tissue and Embryos Bill will give equal recognition to lesbian parents and remove the requirement for a biological father to be named.

The parliamentary committee considering the bill is to publish a report on its findings this week and the bill could become law next year. Critics point out that the legislation will fundamentally change the 200-year-old birth certificate system from a record of parentage to a “social” document.

Figures from the Human Fertilisation and Embryology Authority show the proportion of lesbian couples or single women having donor insemination has increased in the past three years from 28% to 38%. The majority of children created by donor insemination will be in fatherless families by next year.

Infertility clinics say that many of those who present themselves as single women are lesbians who do not wish to attract additional questioning.

“I would say that applies to well over half of those who say they are single. The fact that they are actually gay often emerges during treatment,” said Gedis Grudzinskas, director of the Bridge fertility centre in London, which has promoted the rights of gay women to have families.

In recent years, lesbian couples have converged in different parts of the country. As well as the established gay communities of places such as Brighton and Bristol, there are also now a large number of lesbian families in the suburbs of Manchester and other cities.

The latest data on civil partnerships show that one in four women entering a lesbian partnership has previously been married to a man, indicating that the decline of the social stigma is allowing many more women to express their true sexuality.

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