The British Humanist Association has told the Catholic Education Service (CES) that its 'absolutely outrageous' request that UK Catholic school pupils sign an anti-gay marriage petition may breach the law.
The secondary schools also directed students as young as 11 to a letter written last month that urged Catholic congregations to protect the sanctity of marriage in Britain.
Written by the leader of the Catholic Church in England and Wales, the Archbishop of Westminster, the letter was read aloud to the country's more than a million Catholics who attend mass.
The British Humanist Association believes the CES has likely broken the Equality Act of 2010, which prohibits discrimination against pupils based on their sexual orientation.
The CES's actions are also believed to break the Education Act of 1996 that prohibits 'the promotion of partisan political views in the teaching of any subject in the school'.
However, the Catholic Education Service rejects the suggestion that Catholic schools acted illegally.
'The Equality 2010 Act applied 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,' said the CES in a statement.
The Catholic Education Service negotiates with government on behalf of all bishops to promote and safeguard Catholic interests in education.
The Catholic Education Service confirmed with PinkNews yesterday that at least 359 schools have been contacted.
The CES pointed out: 'The online petition itself makes it clear that people under the age of 16 cannot sign it. We will issue new guidance for our schools to ensure that they are aware of this.'
Conor Marron speaking for pro-gay campaign Coalition for Equal Marriage says: 'Children as young as 11 should not have to be drawn into political arguments such as this, in fact no school pupil should.
'We must protect freedom of religion and freedom of speech, but at all times any duty of care must come first, most especially when it comes to children.'