A significant number of Conservative MPs and some Labour members are set to back an amendment to the Human Fertilisation and Embryology Bill that will retain a controversial requirement.

At present fertilisation and IVF clinics must consider the “need for a father” when deciding if women, including single women and lesbians, can access services.

The bill, which is being considered by the Commons today and tomorrow, replaces that requirement with the need to consider whether the child will be given “supportive parenting.”

Gay rights groups argue that the “need for a father” provision is used to discriminate against lesbians accessing fertility treatments.

Conservatives argue that significant social problems are caused by the lack of a father in a child’s life, and that the legislation sends out a signal that fathers are not important.

Stonewall, the gay equality organisation that has championed this change in the law, rejected that argument.

“By necessity lesbian couples plan very carefully for their families and give careful consideration to the involvement of male role models,” a spokesman said.

“The most important thing for children is to grow up in a stable loving environment.

“Currently more than three million children in Britain are growing up in single parent families. If the bill’s provisions are amended not a single one will gain an additional parent.”

Shadow Health Secretary Andrew Lansley has introduced an amendment calling for the “the need for supportive parenting and a father or a male role model” to be considered by doctors when deciding to treat women.

“It is in the interests of every child to have a mother and a father, but if no father is present, as is, unhappily, the case for many children today, a male role model should be available,” he told MPs last week.

“For that reason, I, personally, do not regard the substitution of “supportive parenting” for “father” as sufficient.

“The reference to the need for a father, which has not been reflected in the code, should be re-cast in the legislation.”

The government’s position remains that given the legal recognition of civil partnerships and laws preventing discrimination on the grounds of sex and sexual orientation, retaining any provision that mentioned a mother and a father is inconsistent with the wider government policy of promoting equality.

Labour MPs have been given a free vote during today and tomorrow’s committee stage on the “need for a father” and two other provisions in the bill – the creation of human-animal embryos for medical research and the creation of so-called “savour siblings,” who would aid a sick brother or sister.

Conservative and Lib Dem MPs have a free vote on all aspects of the Human Fertilisation and Embryology Bill. Last week it was given its second reading by 340 votes to 78, a majority of 262.

However, given the concern among some MPs about the “need for a father,” the vote in favour of that clause, expected tomorrow evening at around 6pm, could be tight.