Christians came together in London on Saturday to hear concerns about the harmful sex education being taught to teenagers and young children in British schools.

The conference, organised by Anglican Mainstream, brought together a broad spectrum of campaigners, including two Muslim parents from Birmingham, where protests were sparked in opposition to the No Outsiders diversity and equality programme.

Concerns among conservative parents of faith have been heightened by the roll-out this September of the Government's new mandatory Relationships and Sex Education curriculum.

Conference delegates heard how schools are increasingly teaching teenagers and even young children about self-stimulation, anal and oral sex, and extreme sexual behaviour.

Dr Lisa Nolland, Convenor of Anglican Mainstream's Marriage, Sex and Culture Group, called current sex education "deeply flawed" and said it "ignores fundamental biological realities, offers false assurance and tacitly encourages children to be sexually active".

"There are major, negative, lifelong consequences to sexual activity which are minimised or ignored in Comprehensive Sexuality Education," she said.

All About Me is a sex and relationships programme that has caused particular alarm among parents in Warwickshire. It teaches children as young as six about self-stimulation, saying: "Now lots of people like to tickle or stroke themselves as it might feel nice. They might play with their hair, stroke their skin or they may even touch their private parts. This is really very normal. However, some people may get cross or say that it is dirty, especially when you touch your own privates. This is strange as it is really very normal, however, it is not polite to do it when other people are about."

The Christian Institute has threatened legal action against Warwickshire County Council over the material.

Will Jones, blogger at Faith and Politics, said: "There is strong evidence that these policies and education programmes are not just teaching children about homosexuality and other identities but they are actively encouraging and causing an uptick in how prevalent they are - it's quite clear that they're becoming fashionable in places [and children] are just to young to be dealing with this."

Rev Lynda Rose, of Voice for Justice UK, said that in spite of Christian morality being presented as outmoded, bigoted "hate speech", current sex education and its emphasis on free love has failed to stem the "epidemic" levels of STIs in Britain, particularly among the young.

In light of the hostility towards the Bible and Christian morality, she said that the strongest weapons in challenging sex education teaching were child protection and evidence of harm.

"Know your facts," she said, as she called on parents to go to schools and insist that they teach children about the health risks of promiscuity.

"Some STIs really are life-changingly horrific and some are becoming untreatable and increasingly resistant to antibiotics, which means they might have the condition for life. How many kids are told this? This is where we need to call schools out because the message that 'if children only use a condom they will be safe' is a lie," she said.

She continued: "Kids are not being told that for some STIs, condoms will not give them any protection because transmission is not by body fluids but skin on skin contact. A condom will not protect against anal or oral cancer.

"Yet this is being promoted in schools as normal. These behaviours are not normal, and a load of evidence proves this beyond all doubt, so go down to your child's school and say: why are you promoting medically hazardous behaviours to children?

"It's supported by all the medical evidence. The facts speak for themselves. So tell schools that yes, you do want children to be prepared for life in modern Britain, we all do. But you want them to learn the facts."

In addition to teaching about the harms of early sexual activity, Rev Rose said that schools should be promoting marriage and monogamy.

"As a society, we could eliminate STIs overnight if we just started to teach children the value of commitment and faithfulness. So go to the schools and demand good teaching," she said.

However, she added that the Church needed to be bolder in speaking out about the misleading teaching in schools.

"The Church needs to stand on our faith, not in bigotry and hatred, but in love," she said.

"There are protections under English law for freedom of speech and we need to claim that more vociferously. There are protections for freedom of religion and we need to stand on that.

"But the Church needs to be bolder in saying: this is our faith. We've got to stop this almost ashamed compromise of 'oh sorry, we're such bullies, we're so horrible, we're so sorry'. We've got to lose that because God has redeemed us in Christ and we need to assert that."

Tom Rogers, Education Manager at the Society for the Protection of Unborn Children, agreed, saying that the Churches had "caved into this agenda", which he said was being underpinned in some cases by "bogus research".

He further argued that the problem of bullying had been "exploited" by LGBT groups to push their agenda in schools.

"It's about an ideological objective, it's not about safeguarding the children, it's not about protecting children from bullying. It's about smashing heternormativity," he said.

Will Jones added that while parents might not want to "rock the boat", it is important that they "get to grips" with what schools are teaching, and engage with it.

"Swat up, do your research, know your human rights as parents to raise your children according to your own philosophy and religion," he said.