The signatories include former Conservative leadership challenger David Davis, ex-ministers Tim Loughton, SirGerald Howarth and Sir Jim Paice, and the former Archbishop of Canterbury, Lord Carey of Clifton.
Former Tory defence minister SirGerald Howarth said that the government had no mandate for such a "massive social and cultural change", which had not been mentioned in the 2010 Conservative manifesto.