A group of concerned mothers in Wales is asking people across the UK to help them launch legal action to stop the rollout of a new compulsory relationships and sexuality (RSE) curriculum.
The RSE Code will be introduced in schools across Wales from September 2022, and will be mandatory for all learners aged 3 to 16.
Controversially, parents do not have the right to opt their children out of the lessons.
Draft guidance has drawn criticism for replacing the word 'sex' with 'sexuality' and omitting references to biological sex.
Kim Isherwood, Chair of Public Child Protection Wales (PCPW), told a meeting of the Marriage, Sex and Culture Group in London on Tuesday that the curriculum amounted to "child abuse" and that parents were being held "over a barrel" that could see them "facing social services" if they refuse to let their children attend the lessons.
PCPW is fundraising to launch a legal challenge against the curriculum. Ms Isherwood said that while the legislation is limited to Wales, it reflects similar curriculums across the UK.
"This is not a Welsh fight or an English, Irish or Scottish fight. It's a UK fight," she said.
RSE has already been compulsory in England since September 2020.
Steve Begoo, head of education at Christian Concern, showed the conference some school resources that teach children to think that Christians are "prejudiced" on the issue of gender and sexuality.
"[The RSE curriculum] is actually confusing, it's inappropriate and it's leading our children to wrong beliefs about their own sexuality," he said.
Mr Begoo warned that the government's proposed conversion therapy ban will leave teachers at risk of being "criminalised" if they do not affirm a child's transgender identity.
He said the onus was on Christians to uphold their legal right to have their children educated in line with their beliefs, and to tell schools that their religious beliefs "are worthy of respect".
"Government guidance is actually in our favour if we use it properly," he said.
He suggested Christian parents might want to consider launching their own schools independent of the state "so that our children, God's children whom we have been given a job to steward, can be trained by Christian teachers who will point them in the right direction and won't hinder them from coming to Jesus".
"Some Christian leaders up and down the country have woken up and the Church has remembered: didn't we used to do education? When did we get the idea that we ask the state to disciple our children?" he said.