A judge in Kentucky has announced he will not preside over adoption cases involving gay parents, saying he does not believe gay adoption is ever in the best interest of the child.

Judge W Mitchell Nance issued an order to all lawyers who practice in his counties, saying that “as a matter of conscience” he believes that “under no circumstance” would “the best interest of the child be promoted by the adoption by a practising homosexual." He informed the lawyers they would have to request a special judge for adoption cases involving gay people.

Same-sex marriage and adoption are legal in all 50 states.

In his order, obtained by The Independent, Mr Nance cites a judicial ethics rule that states judges must recuse themselves from any cases in which they have personal biases. He writes that his "conscientious objection to the adoption of a child by a practising homosexual" could constitute personal bias, and in some cases put his put his impartiality in question.

Lawyers tell USA Today that the judge is “highly religious,” and even opposed to divorce.

Dan Canon, a Louisville lawyer who helped win same-sex marriage rights in Kentucky, said Mr Nance’s decision to recuse himself is in the best interest of children and gay couples.

“It's obviously better that the judge recuse himself from these cases rather than potentially wreck the lives of children who desperately need loving, adoptive parents,” Mr Canon told USA Today.

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But Mr Canon also called it “disturbing” that a judge would reach this conclusion about gay adoption, and added that if Mr Nance “can’t fulfil his duties because of his personal biases, he should resign.”

In an interview with the Courier-Journal, Mr Nance stood by his decision.

"I stand behind the law I have cited, the matter of conscience I addressed and the decision I have made,” he said. He was unable to cite any research proving his position that homosexual couples make inferior parents.

A review of 75 research studies on gay same-sex parents by the Columbia Law School Public Policy Research Portal found that existing studies form "an overwhelming scholarly consensus, based on over three decades of peer-reviewed research, that having a gay or lesbian parent does not harm children."

Mr Nance declined to comment further to The Independent.

“I have said everything in the order that I have to say on the subject," he said.

The Alabama Senate recently passed a law allowing faith-based adoption groups to refuse to place children in homes with gay parents. Senators said the law would allow these faith-based agencies to continue operating in a field where the need is "so high."

"These faith-based agencies have been forced to close their doors because they refuse to place children in homes that go against their faith," Representative Rich Wingo, the bill's sponsor, told Alabama.com. Critics called the bill "prejudice cloaked in religion."