The British government’s announcement of new guidelines for sex and health education across England comes amid a backlash from parent groups who do not want it to be a mandatory part of the curriculum.

Relationships, cybersafety, and mental health are all set to be included as part of the new syllabus in schools across the nation.

Parliament was set to debate a petition on Monday demanding parents retain the right to opt their child out of the classes.

More than 100,000 people have stressed parents’ “fundamental right” to decide when their children are taught the topics. Attendance is set to become compulsory at secondary schools from September 2020.

The Department for Education guidelines create three new subjects – relationships education from primary school, relationships and sex education at secondary school, and health education for all ages.

In what The Guardian describes as a “long-awaited package” of reforms, students will learn about the importance of getting enough sleep, the dangers of sexting and how to spot anxiety in their friends.

Children as young as four will be taught about relationships, staying safe online and the link between physical and mental health.

“Almost twenty years on from the last time guidance on sex education was updated, there is a lot to catch up on,” said the education secretary, Damian Hinds.

“Although sex education is only mandatory to teach at secondary, it must be grounded in a firm understanding and valuing of positive relationships, and respect for others, from primary age.”

“In turn positive relationships are connected with good mental health, which itself is linked with physical wellbeing. So it is appropriate to make health education universal alongside relationships and sex education.”

According to the guidelines, secondary school pupils will be taught about female genital mutilation and other forms of “honor-based” abuse, as well as grooming, forced marriage, and domestic abuse, the DfE said.

Katherine Sarah Godfrey-Faussett, the woman behind the petition, said there are “grave concerns about the physical, psychological and spiritual implications of teaching children about certain sexual and relational concepts”.

Other campaigners are concerned that the reforms could be diluted to appease conservative interest groups. Rachel Krys, the co-director of the End Violence Against Women coalition, is urging the government to launch mandatory teaching on sex and sexuality, gender stereotypes, the law on consent and LGBT equality.

Anna Feuchtwang, chief executive of campaign group the National Children's Bureau, told The Mirror the guidance is “a welcome step forward in preparing children for adulthood, improving their wellbeing and keeping them safe and healthy”.

Former education secretary Justine Greening first proposed the reforms for secondary schools in 2017, but she had said parents would retain the right to withdraw their children from sex education.