Deputy Prime Minister Nick Clegg and Education Secretary Michael Gove have clashed over whether to rewrite sex education guidance.
Mr Clegg, the Lib Dem leader, backs a campaign supported by the sex education lobby and gay groups to modernise the guidance.
But Mr Gove prefers to trust the judgement of teachers rather than burden them with extra directives.
The Department for Education said a Government review had concluded that “the existing guidance offers a sound framework for sex and relationship education in school”.
The Christian Institute has urged caution over any moves to rewrite the sex education guidance.
Spokesman Mike Judge said: “Some people have good motives for wanting to change the guidance.
“They want to address the growing danger of easy access to internet porn, and the impact it has on young people’s lives.
“The Daily Telegraph and some family-friendly groups have got behind that campaign.
“But others have signed up who have a track record of pushing a liberal agenda and sidelining parents.
“Some of these groups, like the Sex Education Forum, want to make the subject mandatory and remove parents’ rights of withdrawal.
“At the moment, the guidance says schools should be neutral on the controversial issue of sexual orientation.
“Groups are claiming that the introduction of gay marriage gives them the green light to rewrite the guidance.
“This issue is a political Pandora’s Box, and the Government should leave the guidance as it is.
“Schools can still tackle issues of internet bullying and online porn, in an appropriate way, without new guidance.”