The Scottish Secular Society and the Catholic Church are at war over the teaching of sex education in schools.

The Scottish Secular Society (SSS) has called on Holyrood ministers to ensure that religious beliefs do not influence the way lessons about sexual health are conducted in the latest draft of its guidance on the subject.

And the campaigners have set their sights on Catholic schools in particular, saying that pupils are being given an "inaccurate and dangerous" view of sexual relations in some classes.

The SSS wants a standardised and mandatory teaching of sex education in all Scottish schools, whether religious or not.

The row is the latest of a series of exchanges between secularists and religious groups, with the SSS being accused of "McCarthyism" and having an "anti-religious agenda" by the Rev David Robertson, the next Moderator of the Free Church of Scotland.

The latest clash is likely to heighten tensions between the groups, with the Catholic Church hitting back by accusing the SSS of interfering with parents' rights.

The Scottish Government is preparing a final version of new guidance on relationships, sexual health and parenthood education (RSHPE) for young people at school, and has sought the views of interested parties.

Garry Otton, secretary of the SSS and author of Religion Fascism: The Repeal Of Section 282, about the abolition in 2000 of the anti-gay Clause 28 of the Local Government Act, said that the Government should not sacrifice children's education "on the altar of religious demands".

He said: "I went undercover in a Catholic school [in Paisley] to witness children bussed in to listen to an American abstinence-only preacher screaming at children that condoms are not safe, telling them that HIV kills you and if they contracted chlamydia just once, there would be a 25% chance they would be sterile for the rest of their lives.

"Much of the information she gave was inaccurate and dangerous. If this is what is masquerading as sex education in faith schools, it must be stopped.

"The Government must not sacrifice children on the altar of religious demands. No presumptions can be made about anyone's sexual orientation or practices, in school or out of it. Every child should receive an appropriate sex education. It is a child's right."

Spencer Fildes, chairman of the SSS, said: "We recognise that some parents, either through concern for the appropriateness of the material taught or through religious stances will wish to opt their child out of sex education.

"However, the consequences for the child of a lack of good sexual education are far-reaching and severe, and so in this case we feel strongly that the right of the child to a good education trumps the right of the parent.

"And it should be mandatory in all schools, religious or otherwise. It is fine to say that condom use is wrong under a faith view, but not to deny the fact that it protects from STDs and pregnancy."

A spokesman for the Catholic Church said that ­Catholic-style education remained ­popular with many Scots, including non-Catholics.

He said: "It's disappointing, though not surprising, that the Scottish Secular Society are so intent on imposing their own views on others that they wish to remove the right of parents to have their children educated in accordance with their beliefs, by suggesting that ­Catholic schools should stop offering the Catholic education which so many parents, many non-Catholics among them, request."

A Scottish Government spokesperson said that it hoped to publish its latest guidance by the end of the year.

She said: "Relationships, sexual health and parenthood education is an integral part of the health and wellbeing area of the curriculum.

"While individual schools may agree arrangements to accommodate teachers' personal views, they remain obliged to offer pupils a full, objective and balanced awareness of all aspects of relationships, appropriate to their age."