Faith schools are using sex and relationship education policies which describe gay sex as “unacceptable” and that homosexuality itself is “disordered”.

An analysis by the National Secular Society of faith school SRE policies also found schools which teach that extramarital sex, contraception and masturbation are wrong, and that using tampons is inappropriate.

The group has warned that plans to give faith schools leeway to teach “in accordance with their faith” will undermine young people’s right to impartial SRE.

The NSS looked at the websites of 634 state secondary faith schools in England between February and April 2018.

Out of the 334 schools where an SRE policy was found, 77 per cent indicated that SRE is delivered according to the teachings of the school’s religious character.

The analysis found various examples of what the NSS called “bad practice” in SRE.

For example, Holy Trinity Academy - a Catholic faith school in Telford - has a policy which says that gay sex is “unacceptable”.

“Homosexual orientation is distinguished from the evaluation of the sexual activity of homosexual people,” the policy states.

“The latter is deemed unacceptable as it does not respect the complimentary nature of male and female since it lacks the life giving potential to proper sexual love.”

Saint John Bosco College - a Catholic school in Wandsworth, London - has a policy which says that homosexuality itself is “disordered”.

It says: “The number of men and women who have deep-seated homosexual tendencies is not negligible. This inclination, which is objectively disordered, constitutes for most of them a trial.”

Sir Robert Woodard Academy, a school in West Sussex with a Church of England ethos, has a policy which forbids the “promotion of homosexuality”.

It says: “Woodard recognises the need to address homosexuality and the need to provide education related to the spread of HIV/AIDS which will, of necessity, include reference to homosexuals, bisexuals and heterosexuals.

“Woodard and the academy will not permit the promotion of homosexuality. Objective discussion of homosexuality may take place in the classroom.”

Some Catholic faith schools have policies teaching that contraception is wrong.

All Saints Catholic School and Technology College in Dagenham, east London, has a policy which states: “The act of sexual intercourse is also the action through which the human race is continued.

“Therefore, any sexual acts where the creation of new life has been deliberately ruled out - including the use of artificial contraceptives - must be regarded as a wrong use of sex.”

The school’s policy says that the Catholic Church does not recognise divorce: “Based on the Gospel teaching of Jesus ‘What God has joined together let no man put asunder’ the Church does not recognise the breaking of the contract of a valid marriage.”

And the policy also warns against against masturbation. “The Church teaches that masturbation is wrong in that it can be seen as a form of self-indulgence,” it states.

“Masturbation encourages us to live in a fantasy world rather than to find fulfilment through working hard at a relationship in the real world. It can teach us to regard others as sex objects, rather than people in their own right.”

Al-Hijrah School, an Islamic school in Birmingham, appears to discourage the use of tampons.

“Among the various types of pads, tampons may not be appropriate due to insertion,” the school’s policy states.

Last year the government legislated to require all secondary schools in England to teach relationships and sex education, but said “faith schools will continue to be able to teach in accordance with the tenets of their faith”.

However, Stephen Evans, chief executive of the NSS, said that basing SRE on religious scripture “can harm young people”.

“All of our students should have the right to access education that will give them clear and accurate information on topics that are so important to their wellbeing,” he said.

“Our report demonstrates that state-funded faith schools are letting young people down in this respect, and it is important that we protect their right to impartial SRE.”