A High Court judge ruled today that a lesbian parent who was not in a civil partnership with her ex-girlfriend does not have to pay maintenance for their child.

The woman, identified only as ‘B’, is not the biological parent of the child and Mr Justice Moylan said she could not be considered its parent because the law differentiates between a ”natural” parent and a legal one.

He said she was a ”social and psychological” mother to the child, the Daily Telegraph reports.

B had won a court order granting her shared residence with the child.

She began a relationship with the child’s biological mother, T, in 1994 and the pair lived together until 2007.

They decided jointly that T would have a child through a clinic with an anonymous sperm donor.

T’s lawyers argued that B must be forced to pay child maintenance because both women continue to take on the role of parents.

However, B’s lawyer Charles Hyde QC said the law did not recognise his client as a parent so she did not have to pay maintenance.

Mr Justice Moylan concluded: “In some respects the outcome in this case may seem objectively surprising.

“However, in my view it is for the legislature to determine who should be financially responsible for children if it is to extend beyond those who are legal parents.

“If I were to extend the definition to include anyone who has acted as a parent, I do not see how I could properly define the limits of such an extended definition in a way which would provide sufficient legal certainty.”