A landmark ruling which gave custody of two children to their biological mother’s ex lesbian partner has been overturned by the Law Lords.

The woman, who cannot be named for the children’s protection, had been granted shared contact of her ex girlfriend’s seven and four year old daughters, until the mother broke the order by moving away, prompting the High Court and the Court of Appeal to grant primary care to the former partner.

But five Law Lords today reversed the decision and ruled in favour of the natural mother, accusing the lower court of being distracted by the case’s “unusual context.”

Lead judge, Baroness Hale of Richmond, said: “The court below have allowed the unusual context of this case to distract them from principles which are of universal application.

“The fact that this woman is the natural mother of these children in every sense of that term, while raising no presumption in her favour, is undoubtedly an important and significant factor in determining what will be best for them.”

She branded the custody battle “as bitter as the disputes which arise between heterosexual couples. And the issues arising are just the same as those which may arise between heterosexual couples.”

Lord Nicholls of Birkenhead said: “A child should not be removed from the primary care of his or her biological parents without compelling reason.”

At the time of the original ruling last April, Lord Justice Thorpe said: “We have moved into a world where norms that seemed safe 20 or more years ago no longer run.”

He asked, “Who is the natural parent?” In the past judges have ruled that the biological parent is the natural parent, ?but in the eyes of the child, the natural parent may be a non-biological parent who, by virtue of long-settled care, has become the child’s psychological parent,” he said.

He decided that since the couple had both raised the children, there was no distinction of a biological relationship.