A CAMPAIGN to ensure all pupils are taught about same -sex marriages at Scottish schools has received political backing.

Representatives from both the Scottish Liberal Democrats and the Scottish Green Party have supported the call from the Humanist Society Scotland.

New guidance on sex and relationships education is currently being drawn up by the Scottish Government to reflect changes in society, such as the legalisation of gay and lesbian marriages.

However, controversy has been sparked by the provision for schools to "opt out" of teaching on same-sex marriages with a continuing provision for religious institutions to take a lead role in denominational schools.

The Humanist Society Scotland has argued against the continued opt-out, stating: "It is no longer acceptable that religious bodies have a say in the sex and relationships education of children - evidence from our health boards show that this is failing our young people."

Patrick Harvie, MSP for Glasgow and co-convener of Scottish Greens said: "All young people deserve a right to inclusive, evidence-based education on relationships, sexual health and parenthood."

Alison McInnes, Liberal Democrat spokeswoman for justice, added: "It is time for all children in Scotland to be given access to a programme of sexual health and relationships education."

However, Michael McGrath, director of the Scottish Catholic Education Service, said the body supported the rights of all teachers who have ­conscientious objections to be required to endorse and promote the redefinition of marriage within the new legislation.

He added: "It cannot be right to force teachers to promote a vision of marriage which is at odds with their own sincerely held views or beliefs."

A Scottish Government spokesman said sex education was an integral part of the curriculum, adding: "While individual schools may agree arrangements to accommodate teachers' personal views, they remain obliged to offer pupils a full, objective and balanced awareness of all aspects of relationships, appropriate to their age."

The guidance is expected to be shared with schools by the end of the year.