Even though the man, known only as Steve, isn't Catholic he's been told his children must go to church if they are with him.
Judge James Orrell imposed the order during a hearing at a court in the Midlands which show he discussed his own Catholic faith during the hearing to decide contact arrangements for Steve's two sons.
His ex-wife is Catholic and has not been subjected to the order which said: "If the children are with their father at Christmas he will undertake that they will attend the Christmas mass."
Steve, 51, told the Telegraph newspaper: "It's all very bizarre. This aspect of the contact order was not requested by the other side in the case.
"The judge decided that I would commit to taking the children to mass and he put it in the court order.
"What I think is really concerning is that it does not allow me or my children any freedom of religious expression.
"I am definitely not Catholic. The last time I went to church was some time ago and it was a Unitarian church that I attended.
"My oldest son, who is now 10, has already expressed a clear lack of belief but legally I am required to take him to Roman Catholic mass at Christmas.
"Because my contact arrangements now give me the children on some weekends, I am concerned that I will now also be required to take them to mass on Sundays when they are with me, even though that is not part of the original order."
The ruling has faced a number of legal challenges since 2009 but is still in force.