A Christian magistrate told an employment tribunal he quit family court duties because he does not agree with adoption by gay couples.
Andrew McClintock says he could not place children with gay couples
Andrew McClintock, who had served in the family courts in Sheffield for 15 years, said civil partnership laws clashed with his religious beliefs.
He said he might have had to sanction the removal of a child from its natural family into the care of a gay couple.
Mr McCormick, 63, said his request to avoid such cases had been refused.
That left him with no option but to resign, he claimed.
Mr McClintock, a member of the Christian People's Alliance Council, said new rules on same-sex couples contradicted both his personal religious beliefs and his duty as a magistrate to put the child's welfare first.
Last year Mr McClintock, a former manager in the steel industry and now a self-employed logistics consultant, said he thought it was wrong for the government to use disadvantaged children as "guinea pigs".
He said placing them with gay couples was an "experiment in social science".
The tribunal, which began in Sheffield on Wednesday, heard that Mr McClintock placed "severe conscience issues" on him and his fellow magistrates.
In a statement read by the tribunal panel, father-of-four Mr McClintock said: "Many of the new legislative initiatives appear directly contrary to both common sense and the accepted principles of Judeo-Christian morality.
"It has placed severe conscience issues on me and on my fellow magistrates. It is necessary for a stand to be made in order to maintain the integrity of the administration of justice."
His case is being heard as the Roman Catholic church mounts a campaign to be exempt from laws on adoption by gay couples.
Catholic leaders in England and Wales said its teaching prevented church adoption agencies placing children with homosexuals and they would have to close if bound by the rules.
The move by the Catholic church has been backed by the Church of England.