"Children should have two legal parents when adopted by people in long-term relationships." said the British Agencies for Adoption and Fostering (BAAF) yesterday in evidence to the select committee on the adoption and children bill.

"We believe it is inappropriate to use adoption as a means of promoting the importance of marriage, if this has the effect of denying children, who are already disadvantaged, the opportunity of the joint legal and lifetime commitment of two parents," said BAAF chief executive Felicity Collier.

"It is estimated that 40% of children are born outside of marriage and that a similar proportion of adults live in committed relationships. If we restrict joint adoption to married couples, we can only reduce the opportunity for children to find adoptive parents."

She said that social workers would take into account the stability and longevity of any relationship when assessing prospective adopters.

Conservative select committee member Caroline Spelman said married couples were more likely to offer a permanent two-parent home: "The evidence shows that, if we are worried about permanency, married couples tend to stay together longer."

Labor MP David Hinchcliffe, committee chairman, stated that: "From a personal point of view, I can see the concern over where you have a child placed with unmarried foster carers and it may be deemed in their best interests to be adopted by both." But he added. "I am not advocating lesbian and gay adoption - nor unmarried adoption, for that matter."

BAAF also called for amendments to introduce a national system of financial support for adoptive parents and a register of private, informal fostering by friends and relatives.