The Government has been accused of being "obsessed with trying to force ever younger children to learn sex and relationships" after MPs this week approved the expansion of sex and relationship lessons that will teach primary-age school children about LGBTQ relationships.
The draft Relationships Education, Relationships and Sex Education and Health Education (England) Regulations 2019 were approved in the Commons on Thursday by 538 votes to 21.
If the regulations are approved by the House of Lords, then from September 2020, primary school children will learn about different forms of family, while lessons for secondary age school will cover sexual orientation and gender identity.
Colin Hart, Chairman of the Coalition for Marriage, said the plans risked "downgrading marriage" while the restrictions on opting children out of the lessons were effectively "sidelining parents".
He urged education secretary Damian Hinds to "think again" on "imposing these lessons on all".
"This is a disappointing result that continues the tyranny of the Department for Education, which is obsessed with trying to force ever younger children to learn sex and relationships, even when it is not age appropriate and goes against the wishes of parents," he said.
"It waters down the importance of marriage, which children should be taught, by traducing the Institution to just one form of many different types of relationship.
"It ignores the fact that traditional marriage matters. Traditional marriage is the most stable form of relationship and research shows that stability is important for the healthy development of young people."
The draft regulations require that schools consult with parents about the contents of the sex and relationship lessons, which should also be "appropriate having regard to the age and the religious background of the pupils".
However, the limited right of parents to opt their children out has proved contentious for parents of faith.
While requests to withdraw children at the primary school level will be automatically granted, at secondary school the rules change and parents will only be able to opt their children out up to the age of 15, unless the head teacher believes that such a request should not be granted. After the age of 15, opted out children can choose by themselves to participate in the lessons.
Tory backbencher Sir Edward Leigh was among those voting against the plans on Thursday. He has been an outspoken critic of the proposals and previously said they represented a "fundamental shift of power to the state".
"All previous Conservative Governments have given an untrammelled right to parents to remove their children from sex education," he said.
"But here in certain circumstances that right has been transferred to the headteacher."
The draft legislation was passed as Muslim and Christian parents continue to protest against equality lessons at Parkfield Community School in Birmingham.
Hundreds of parents have withdrawn their children from the lessons taught by the "No Outsiders" programme, which cover same-sex relationships.
They are demanding that No Outsiders be scrapped by the school, which has a largely Muslim student population.
The school has temporarily suspended the lessons in the wake of the protests.
The lessons were introduced at the school by assistant head teacher Andrew Moffat, who is gay. He told BBC WM, that there were "misconceptions" about what the No Outsiders lessons teach.
"People are worried about the way the government are proposing to change sex relationship education in the UK and people are mixing that up with No Outsiders," he said.
"No Outsiders isn't about sex education. It's about community cohesion, British values, it's about people getting along and co-existing."
Free Church of Scotland minister the Rev David Robertson, however, said that Christians should stand with Muslims on this issue.
"Despite the claims, this is not about diversity. It is in fact the very opposite," he wrote on his blog.
"This is about imposing one, and only one, sexual/relationship philosophy upon everyone. They don't want diversity. They will not allow Muslim parents (or Christian) to have their children brought up in their faith.
"We must all be brought up in the secular humanist faith and whatever its celebrants tells us at any particular time is moral or 'on the right side of history'."
He continued: "Homosexuality is not the issue here. There are far deeper and much more profound issues. Not least the freedom for us, and our Muslim brothers and sisters, to bring up our children, without being dictated to by the political elites who seek to impose their bourgeoise morality on our children. On this issue Christians and Muslims stand together."