The number of teachers facing abuse on social media from pupils and parents has more than doubled in 12 months, according to a survey of trade union members in the profession.

School staff are being confronted with sexist, racist and homophobic remarks, as well as offensive comments about their appearance, competence in the classroom and malicious slurs, the study suggests.

In one case, a photo of a teacher was posted online with the word “bitch” underneath, while in another, pupils used the name of a heavily-pregnant school worker to post insults, the teaching union NASUWT said.

There have also been examples of parents hurling abuse through social media, including personal comments about teachers or their families.

NASUWT said the figures, released the day before the union meets for its annual conference in Cardiff, were deeply worrying.

Overall, 60% of the almost 1,500 NASUWT members polled said they have had comments or information posted about them on social networks, related to their work as a teacher. This is up from 21% in 2014.

Of these, nearly half (48%) said these remarks were posted by pupils, 40% said they were put up by parents, and 12% said both parents and pupils were responsible.

The findings show that 62% said pupils had posted insulting comments, while just over a third (34%) said students had taken photos or videos without consent, a third (33%) received remarks about their performance as a teacher, 9% had faced allegations from pupils about inappropriate behaviour and 8% had been subjected to threatening behaviour.

While over half (57%) of pupils responsible were aged between 14 and 16, 38% were aged between 11 and 14, the teachers’ poll found, a fifth were 16 to 19, and 5% were seven to 11.

Among the examples published by NASUWT was the case of a student uploading a teacher’s photo and then, along with classmates, writing “bitch” and “twat” underneath. One teacher said they were harassed for nine months by students who sent sexually explicit messages and set up a fake social media account in their name.

The union said it had been told of a teacher receiving the comment “I hope she gets cancer”, while the heavily-pregnant worker had faced remarks such as “ugly f****** bitch” as well as having an account established in her name.

Of those who said they had been abused online by parents, the vast majority (64%) received insulting comments or remarks about their performance in the classroom (65%).

One parent told a teacher through social media that they were “rubbish” and a “bitch” who tried to kill their daughter by making her do PE and not allowing her to use her inhaler. The teacher concerned said this was untrue.

Another school worker faced comments from a pupil’s family member about how they looked and that they were ugly.

NASUWT general secretary Chris Keates said: “It is deeply worrying to see that the abuse of teachers has risen by such a huge margin this year.

“Equally concerning is that it appears that more parents are the perpetrators of the abuse. The vile, insulting and personal comments are taking their toll on teachers’ health and wellbeing and undermining their confidence to do their job.

“Many teachers tell us that they suspect they are being abused online but dare not look, for fear they could never walk into their school again to have to face their abusers,” she said.

“While there has been some improvement in action taken on reported abuse, there are still too many cases where no appropriate action is taken and teachers are being left devastated, humiliated and traumatised.”

Keates called for the next government to take the issue seriously and to require schools to have a zero-tolerance policy and use all sanctions available to address abuse of staff.