Catholic schools in Wales have been reminded to give a balanced perspective when discussing same-sex marriage.
Welsh Government minister Leighton Andrews has written to headteachers after the Catholic Education Service (CES) invited pupils to sign a petition opposing laws on gay civic marriage.
Mr Andrews said his intervention came about because the CES's campaign was political.
Under the Education Act 1996, both sides of a political argument must be discussed in classes for pupils aged 12 and under.
The CES insists it has not broken the law.
Labour AM Mr Andrews told fellow politicians in the Senedd about the matter through an official statement.
He wrote: "Members will be aware of recent coverage in the media concerning a letter dated March 10 from the Archbishop of Westminster and the Archbishop of Southwark and issued to all Roman Catholic secondary schools in England and Wales via the Catholic Education Service."
"The archbishops' letter set out the Roman Catholic Church's vision of marriage, which focused on the relationship between a husband and wife. In a covering email, headteachers were asked to consider asking staff and pupils to themselves consider signing the Coalition for Marriage's online petition to support the existing definition of marriage."
Mr Andrews said a website had made it clear that the petition was intended for signature by those "aged 16 or over", but the original email had not.