A lesbian has won a landmark High Court ruling securing access to an infant following a bitter dispute with her ex-partner.

The woman, who cannot be named for legal reasons, was denied access when the birth mother left Britain with the baby and returned to her native Ireland.

The High Court heard that the woman – referred to as ‘L’ – artificially inseminated her partner with an anonymous donor’s sperm during their 18-month relationship.

She considered herself an “equal parent”. However, her name did not appear on the infant’s birth certificate.

After the couple split, the birth mother ‘C’ left Britain for Ireland, taking the baby with her.

The birth mother resisted L having any relationship with the baby, who is now six months old.

Yesterday, Mr Justice Peter Jackson ruled that L’s role in the conception and the loving care she gave her meant that she is the child’s “psychological parent”.

She was then “constantly on-hand” to care for their “much-wanted” baby, and took over breastfeeding for 10 days when the birth mother fell ill.

Mr Justice Jackson said the case was an example of “the painful legal confusion that can arise when children are born as a result of unregulated artificial conception.”

He added L had been “as involved as she could have been” in the plan to have a child, the conception and in caring for G after her birth.

The ruling, which broke new legal ground, has paved the way for L to fight for joint residency of the child.

The court heard L and C thought of themselves as “equal parents”, but there was no talk of legal rights at the time of conception. L twice tried, but failed, to get her name on the birth certificate.

Although G’s surname is a combination of both women’s, L was told by a lawyer that she had “no legal rights” over the child.

The judge said the couple’s 18-month relationship was “fraught with difficulties”.

Same-sex couples who conceive in a clinic are given forms to sign, making them both legal parents.

For those who carry out the procedure at home, only the birth mother is the legal parent – the other must file for adoption.