The legalization of gay marriage cannot change Christian teaching on sexual morality, and the Catholic Church cannot accept marriages of same-sex couples, the bishops of England and Wales said in a document distributed in parishes July 27-28.

Catholics must “accept their calling” to be “out of step with popular culture” and “to live faithfully by the teaching we have received,” said the document, titled The Narrow Gate.

The Marriage (Same-Sex) Couples Act became law July 17 and opened the door for same-sex marriages to occur as early as summer 2014.

Upholding Church teaching that all sexual activity outside of the legitimate marriage of one man and one woman is sinful, the bishops’ document stressed that marriage is a lifelong, faithful commitment “ordained by nature and by God for the creation of the family and future generations.”