The Church of England has been accused by gay rights campaigners of orchestrating a "masterclass in melodramatic scaremongering" after it warned that same sex marriage could threaten its relationship with the nation.

Ben Summerskill, chief executive of Stonewall, the campaigning gay rights group, dismissed fears raised by the Church of England that introducing same sex marriage would undermine its centuries-old role as the established Church.

He said polling commissioned by Stonewall has shown more than 80% of people in Britain under 50 are in favour of introducing same sex marriage - amongst religious people, he said, three in five said gay people should be able to get married.

"That holes below the water line the tendentious claims being made by a small number of clergy," he told BBC Radio 4's Today programme.

"Many bishops in the Church of England today will be rather pleased because once again they are not talking about global poverty or the HIV pandemic - they are talking about the subject that obsesses them, and that is sex.

"I have not come across such a masterclass in melodramatic scaremongering - that somehow this is the biggest upheaval since the sacking of the monasteries - since as a journalist myself a decade ago I was summoned to a government briefing to be told about weapons of mass destruction in Iraq."

Mr Summerskill's remarks come after the Church of England said that introducing gay marriage would threaten the establishment of the Church of England and lead to an unprecedented clash between its own canon law - that marriage is between a man and a woman - and that of Parliament.

The Church also warned that in spite of ministerial assurances that churches would not have to conduct gay marriages, it would be "very doubtful" whether limiting same-sex couples to non-religious ceremonies would withstand a challenge at the European Court of Human Rights (ECHR).

A successful legal challenge brought at the ECHR could make it impossible for the Church of England to continue its role conducting marriages on behalf of the state, it said.

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