A US judge has ruled Florida's gay adoption ban is unconstitutional.

The remark came in a case where an openly gay Key West foster parent is trying to adopt a 13 year old boy he has raised since 2001.

The teenager, who has learning disabilities and special needs, is currently cared for by his 52-year-old foster father.

A social worker recommended the guardian and his partner be allowed to adopt the boy, because they provided a "loving and nurturing home", "fair and consistent" discipline and were financially secure.

The foster father was appointed guardian for the boy in 2006. Recently the boy had told a hearing that he wanted his guardian to adopt him.

When asked why, he said: "Because I love him.”

Declaring the adoption to be in the boy's "best interest,” the Monroe County judge said the Florida law forbidding gays and lesbians from adopting children is contrary to the state constitution.

David J Audlin Jr said it “singles out a group for punishment.”

"Contrary to every child welfare principle," the judge wrote in his summary, “the gay adoption ban operates as a conclusive or irrefutable presumption that ... it is never in the best interest of any adoptee to be adopted by a homosexual.”

Florida is one of only two states - including Mississippi - that forbid gay people from adopting children.