Parents and pupils are using social media to publicly insult and abuse teachers, leaving them traumatised and risking their health, a union said today.

An NASUWT survey of 7,500 teachers found that 21 per cent had had negative comments posted about them on the internet.

One pupil used Twitter to tell a teacher: “You are a paedo and your daughter is a ***.”

Another set up a bogus Facebook account in a teacher’s name, writing: “I will rape every Year 8 pupil who comes to the school.”

The union said such “highly offensive” and abusive language was common, including comments about teachers’ appearance, competence, and sexuality.

Chris Keates, NASUWT general secretary, said: “Steps need to be taken to protect teachers from the abuse of social media by pupils and parents.

“Teachers are often devastated by the vile nature of the abuse they are suffering. Some have lost their confidence to teach once they see foul and personal remarks made by pupils in their classes and have left the profession.

“Others have been so disturbed by the comments that their health has been affected.”

The survey found that 64 per cent of the teachers abused on social media had had comments posted by pupils, 27 per cent by parents, and 9 per cent by students and parents.

One parent publicly told a teacher who was not a British citizen to “go home”. Others were racially abused.

More than a quarter of the teachers who reported comments on the internet said that videos or photos taken without their consent had also been posted.

When social media abuse was reported to the police no action was taken against the pupils or parents in more than three quarters of cases, the survey found.

Ms Keates said: “Schools need policies which prevent abuse and identify sanctions which will be taken against parents and pupils who abuse staff in this way. Schools should also be supporting staff in securing the removal of the offensive material from social media sites and encouraging the staff concerned to go to the police.”

The union also said that teachers were being “swamped” with work related emails from senior staff outside school hours. Nearly half of teachers in the survey said there was an expectation that they would respond even though they were not supposed to be working.

One teacher said they were expected to write pupil reports while off sick. Another said they had had “bullying emails” after 11pm, asking for work the next day. There was also a report of a school encouraging parents and pupils to email teachers with any concerns and another where teachers where expected to communicate online with pupils in the evening.

The union said such practices represented “home invasion on a grand and unacceptable scale”.