Members of a major education union have attacked the Sexual Orientation Regulations for not banning faith schools from teaching that homosexuality is a sin.
Delegates at the annual conference of the University and College Union called on tougher guidelines on how children are taught.
The union does not represent primary or secondary school teachers but lecturers in further or higher education.
UCU has more than 116,000 members and is the largest such union in the world.
Delegates voted unanimously to call for an end to negative characterisations of gay lives.
Some members argued that the right of faith schools to teach their religious beliefs about homosexuality meant that the Sexual Orientation Regulations were compromised.
The SOR became law at the start of May and make it illegal to discriminate on the grounds of sexual orientation when providing goods and services. Schools are covered by the new rules.
Alan Whitaker, a delegate from Oxfordshire, told the conference:
“The regulations actually say that there is nothing to stop teachers proclaiming the superiority of heterosexual marriage.
“The regulations say it’s unlawful to characterise same-sex relationships as inferior. But to my mind it’s rather difficult to see how you can do the one without implying you are doing the other.
“If attitudes are to change that will come about as a result of education.
“And that makes it vitally important that teachers do not instil negative images of same-sex relationships and transgender people in those that they teach.”
Government guidance says that teachers may tell pupils of their religious beliefs about homosexuality, and that faith schools can teach that it is a sin.
Hugh McKinney, chairman of the National Family Campaign, told the Daily Mail:
“There are differing views on how marriage should be taught in schools and this has to be fair all round.
“There should be an opt- out available for faith-based schools to allow teachers to teach what has traditionally been the case in the UK, and to reflect the majority of the population, regardless of orientation.
“The legislation has only just been passed so we don’t actually know the legality or otherwise of any set of teaching at the moment.”