Schools in England will be banned from teaching sex education to children under nine, under government proposals.

The BBC has not seen the new guidelines but a government source said they included plans to ban any children being taught about gender identity.

If asked, teachers will have to be clear gender ideology is contested.

Statutory guidance on relationships and sex education – which schools must follow by law – is currently under review.

The National Association of Head Teachers has previously raised concerns the review is “politically motivated”, saying there is no evidence to suggest a widespread problem with pupils being presented with age-inappropriate materials.

The review was announced by Prime Minister Rishi Sunak following concerns that some children were being exposed to “inappropriate content”.

The government believes that clearer guidance will provide support for teachers and reassurance for parents.

The proposals, which are expected to be announced on Thursday, will set out which topics should be taught to pupils at what age.

It is mandatory for relationships, sex and health education to be taught in all secondary schools in England, while relationships education has been compulsory for primary schools since September 2020.

Under current guidance, external, it is down to primary schools to decide whether they need to cover any aspect of sex education to meet the needs of their pupils.

Last year more than 50 Conservative MPs wrote to the prime minister claiming children were being “indoctrinated with radical and unevidenced ideologies about sex and gender”.

Separate guidance published last year stated teachers should inform parents if their child wished to change their gender identity at school.