The two year old boy is waiting for a new family after a court made the decision he should be removed from his parents.
His current mother had argued in court that a couple selected to look after him were not suitable because they were Christian and not a "religious match".
But the judge dismissed that saying it wouldn't be possible to get a "perfect" match but that religion doesn't "trump" other "positive" factors.
The case has just emerged in a written ruling by the judge published on a legal website.
It did not specifically say what religion the mother was although it is suggested she is Muslim.
The new adoptive family were originally Muslim but have converted to Christianity.
Judge Simon Wood was sitting at a family court in Newcastle upon Tyne when he made the decision.
He made an order placing the little boy for adoption 13 months ago after finding that he had been "emotionally abused" and living in a "volatile and violent" family with "seriously sub-standard parenting".
The judgement said that one of the boy's family did not attend the hearing because they were "at Mecca".
"[The little boy] has ... been formally matched with a couple who are said to be practising Christians, having converted from Islam," said Judge Wood
"That lack of religious match is something that is raised before me."
He said a "perfect match may be unachievable" and added: "Culture in its widest sense, but also including religion, was but one factor that would not trump other factors if they were all positive."
Dr Krish Kandiah, head of Home for Good, a charity encouraging Christians to adopt, told Premier's News Hour: "I understand the kind of religious liberties aspects of this but in the interests of the child I think it's better that a child gets a placement with a family that's going to love them and be a safe and protective environment for that child.
"Even if the perfect match of religion and ethnicity isn't possible."
Dr Krish Kandiah speaking to Premier's Marcus Jones on the News Hour: