Image caption Mr Gove is to follow the Welsh government's lead and examine claims against the CES

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 It was just a really outdated, misjudged and heavily biased presentation."

In March, the Catholic Church in England and Wales set out its opposition to gay marriage in a letter which was read out or handed out at Sunday Masses. It was also circulated to Catholic secondary schools.

"The letter is a positive affirmation of marriage, as is the Coalition for Marriage (CFM)'s online petition," said a CES statement.

"As the letter says, Catholics believe that 'marriage is a high and noble vocation'. We reject the suggestion that Catholic schools have acted illegally. The Equality Act 2010 applies to all schools and we are fully supportive of the Act.

"It is central to Catholic teaching that all individuals should be treated with respect and dignity.

"Catholic state schools have always been permitted by law to teach matters relating to sex and relationships education, including the importance of marriage, in accordance with the teaching of the Catholic Church."

The CFM online petition has more than 470,000 signatures.

CES says it is only intended to be signed by people over the age of 16, and the age restriction would be stressed in any future correspondence with schools.