Education Secretary Michael Gove is to examine claims the Catholic Education Service (CES) broke impartiality rules on the topic of gay marriage.

It emerged this week that the CES wrote to nearly 400 state-funded Roman Catholic schools inviting them to back a petition against gay civil marriage.

Schools and teachers are forbidden to promote one-sided political arguments. The CES has denied breaking any laws, saying Catholic views on marriage are religious, not political.

On Thursday, the Welsh government said it was to investigate similar complaints against the CES.

"Schools have a responsibility under law to ensure children are insulated from political activity and campaigning in the classroom," said a Department for Education spokesperson.

"While faith schools, rightly, have the freedom to teach about sexual relations and marriage in the context of their own religion, that should not extend to political campaigning.

"Officials are looking into this as ministers are anxious to establish the full facts of this case and will be meeting representatives of the CES shortly."

Earlier this week, Pinknews.co.uk reported that students at St Philomena's Catholic High School for Girls in Carshalton were "encouraged" to sign the anti-equality pledge by the school's headmistress.

"In our assembly for the whole sixth form you could feel people bristling as she explained parts of the letter and encouraged us to sign the petition," a pupil was quoted as saying.

"She said things about gay marriage and civil partnerships being unnatural. It was just a really outdated, misjudged and heavily biased presentation."