For the first time guidelines on self-harm will include schools and prisons in England and Wales which will help teachers and officers protect more vulnerable people.

The advice shared by the National Institute for Health and Care Excellence (NICE) will run until 1 March.

A study conducted in 2017 suggested 7 per cent of girls and at least 3 per cent of boys aged between 11 and 16 are more likely to self-harm, but professionals are concerned the number is higher with many children hiding their mental health conditions.

Prof Nav Kapur is an adviser on the guidelines and professor of psychiatry and population health at the University of Manchester.

Kapur said: "Self-harm can occur at any age and present to any setting.

"This new guideline is an opportunity to make things better, particularly from the point of view of assessment and aftercare."

The new guidelines advises anyone who expects someone is suffering from mental health to organise a psychosocial assessment by a mental health expert as soon as possible.

Data collected the assessments help professionals understand what made the person self-harm and ensure they receive the correct care and sharing the information with their families.

Dr Paul Chrisp, from NICE, said: "It is important that our committee has made recommendations for education and criminal justice settings.

"Data in the past few years has shown that people working within these sectors would benefit from clear guidance about how they should help someone who is self-harming.

"These guidelines set out a way for every person who self-harms to be able to get the support and treatment they need."

Emma Thomas, from YoungMinds charity, said lockdown "had a disproportionate impact on this age group"

"Prior to the pandemic, one-third of schools did not provide any in-school mental health support, so we are calling on the government to invest in the further rollout of these teams and other schools-based mental health support."

One in five girls and one in 10 boys aged between 17 and 19 have self-harmed or attempted suicide according to a 2017 survey.