Sex and relationships education is to be compulsory in all schools, the government is expected to announce shortly.

All children, from the age of 4 upwards, will be taught about safe and healthy relationships, the education secretary, Justine Greening, will tell Parliament. Children will also be taught, at an appropriate age, about sex.

The decision follows a widespread campaign by charities, MPs and local authorities, calling for sex and relationships education (SRE) to be made a statutory part of the curriculum.

Until now, basic sex education - limited to teaching children about sex in biology lessons - has been compulsory only in schools run by local authorities. Academies and free schools, which are not under local authority control, do not have to follow the national curriculum, and are therefore not obliged to teach the subject.

The new changes - to be announced in a written statement from Ms Greening -  will represent the biggest overhaul of sex and relationships education in 17 years.

Tackling ‘sexting’

The government is expected to announce a new SRE curriculum, which will be introduced to every primary and secondary in England, including academies, free schools and independent schools.

The curriculum is expected to include issues such as online safety, sexting and consent. It will also tackle domestic abuse and sexual harassment.

The announcement will be made as an amendment to the Children and Social Work Bill, as soon as this afternoon. It is expected that parents will still have the right to withdraw their children from the lessons in all state schools.

At the end of last year, the chairs of five different Commons select committees called on Ms Greening to make SRE a statutory subject. Their demand came after a report from the Women and Equalities Committee showed that sexual bullying was endemic in schools.

A ‘ticking time bomb’

Earlier this month, these calls were echoed by the Local Government Association, which referred to the lack of SRE in some schools as “a ticking sexual-health time bomb”.

The association pointed to the high number of sexually transmitted infections (STIs) diagnosed in teenagers and young people.

And, this week, a survey commissioned by the charity Plan International UK showed that 75 per cent of British adults wanted children to be taught in school about the impact of pornography. In addition, 71 per cent wanted pupils to be able to discuss sexting in school.

Last month, Green Party co-leader Caroline Lucas proposed a Bill that would make personal, social, health and economic education (PSHE) compulsory in all state-funded schools. However, Conservative MPs made lengthy speeches about the preceding Bill on the day’s agenda, leaving Ms Lucas fewer than five minutes in which to discuss her draft legislation.

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