The Act, which came into force on 30 December, means that unmarried couples in England and Wales, including gay and lesbian couples, are able to adopt jointly. Up until now only married couples or single people could apply to become adoptive parents, so that, where a single adopter was living with a partner, only one adult was recognised as the legal parent. This important change means that where two people are living in a secure and stable relationship, both adults can become a child's legal parents. It is hoped that this will encourage more adopters to come forward which will help the many children waiting for families; it will allow the permanent partner of a current single adopter to apply to be the child's adopted parent as well which will recognise the role of this partner in the child's life.

The new Act also introduces special guardianship orders which give foster carers, relatives and others caring for a child, the opportunity to apply for a special guardianship order which is expected to last until the child is 18 and will mean the child is no longer the responsibility of the local authority.

Other changes include giving birth mothers and other birth relatives the legal right to ask for an intermediary service to trace an adoptive adult and find out if contact would be welcome. In the 1950s and 1960s when it was socially unacceptable to have an illegitimate child many unmarried mothers felt they had no choice but to give up their baby for adoption. For many of these mothers it will be possible, for the first time, to find out how their adopted child is and possibly to make contact. Up until now, a number of adoption agencies and local authorities have provided these services, but availability has been patchy and inconsistent. No information about an adopted adult's identity or location will be given without their consent and they can register a "veto" if they do not want to be contacted.

Felicity Collier, BAAF chief executive, said: "These changes will have a major impact on thousands of families. We know there are people eagerly awaiting the 30th December because they are an unmarried couple who would like to adopt jointly, because they are fostering a child and want to make sure the child can stay with them for the rest of their childhood or because they would desperately like know more about a child they gave up for adoption many years ago.

"We welcome the fact that no identifying information about adopted adults will be given without their consent but we believe there are many adopted adults who have not made the first approach in case it is not welcomed by their birth parent but who would want to respond if they knew their birth parent was concerned to know how they were.

"Opening up adoption to unmarried partners will encourage more people to consider adoption and this is very important at a time when too many children wait too long in temporary care waiting for an adoptive family or, in some cases, never have the chance of adoption at all.

"Foster carers often want to make a permanent commitment to a child whom they love and are caring for but for one reason or another it is not right to legally sever the child from their birth parents through adoption. Special guardianship will give the child much greater security about the future and we welcome this major new order."

She adds: "BAAF campaigned for many of these changes and is delighted they are now coming into force."