A gay man and a lesbian couple have been embroiled in a complex and unprecedented legal battle in the Court of Appeal of England and Wales over access to their two children conceived through artificial insemination.

In June this year a lower court awarded the sperm donor father joint residency, under which he has equal access to the children including 152 overnight stays. In seeking to overturn the decision, the couple, who cannot be named for legal reasons, have asked the court to acknowledge them as the children's primary carers by requiring the children to keep permanent residence at their address.

From the outset the father had 'parental responsibility' for the children, which gave him legal ground to seek further access. The outcome of this highly controversial case may clarify the rights and responsibilities of sperm donors who donate outside of licensed clinics and impact upon issues of shared residency.

The man donated sperm twice to the lesbian couple resulting in the birth of their son and daughter, aged nine and seven respectively but the relationship between the donor and the recipients broke down. Counsel for the women, June Venters, QC, told the court the children were 'aware of the difficulties between mummy and daddy'. She submitted that the women recognised a meaningful relationship existed between the children and their father and were not suggesting severing contact with him entirely, but the children needed to know which was their permanent home and 'who we all are in their lives'.

Ms Venters argued that a residency order should be made in favour of the lesbian couple who have been the children's primary carers since birth. Ms Venter told the court the current contact arrangements were 'enormously complex', and it was in the children's best interests that their day-to-day management lay with the two women. She also said the original order marginalised the mother's partner, to whom she has been married for twenty years.

Alex Verdan, QC, representing the father, submitted that the man had always made clear his wish to be involved in the children's lives and the women had made 'a very hostile application' to strip the father of his parental rights. Moreover, the father played a central role in his children's lives, including taking them to the doctor and paying their school fees. Mr Verdan impressed upon the court that 'this is not a case of two mummies'.

The case has attracted interest from both legal circles and interest groups, including fathers' groups. The latter would like shared residency (meaning both parents have joint responsibility for their children and must consult on key decisions, but not necessarily that the children reside equally with both parents) to become the norm after parents separate and are hoping that any subsequent law reform will support this stance.

The appeal was heard by the Master of the Rolls, Lord Neuberger of Abbotsbury, Lord Justice Patten and Lady Justice Black, who have reserved judgment for a later date.