The finding comes from a study comissioned by the Teacher Support Network, published as the TES Magazine begins a four-part series on bullying and the ways in which teachers can tackle it in the staffroom as well as the playground.

The network, which provides a support helpline for teachers, worked with Glamorgan University to question 541 teachers about victimisation in the workplace.

They found that more than one- quarter of teachers felt they were regularly presented with an unmanageable workload. Six other key types of behaviour they viewed as victimisation were: having their opinions ignored; exclusion from discussions; having information withheld; facing a hostile reaction; persistent criticism; and being repeatedly reminded of their errors.

Patrick Nash, chief executive of the Teacher Support Network, said the figures were “quite shocking”. Although school leaders and staff were experiencing increased pressure, this was no excuse to bully.

“There are more and more anti-bullying policies for children,” Mr Nash said. “But these are supposed to apply to staff, as well.

“In schools that do well, there’s a culture that people can talk about what is and isn’t appropriate. But those conversations don’t happen enough.” Mr Nash urges teachers not to confront bullies on their own but to seek support from their union to deal with it.

Secondary school teacher Laura, 38, from South Yorkshire, told TES Magazine she had endured excessive workloads, unrealistic deadlines and being undermined in front of pupils. “It has destroyed my life,” she said.

Brian Lightman, president of the Association of School and College Leaders, questioned whether the word “bullying” was always appropriate. “Heads might pass work on to other people, not realising the pressure it puts them under,” he said. “We’d encourage teachers to discuss problems with senior members of staff”.

For advice on tackling bullying read the four-part series starting this week in ‘TES Magazine’, or visit www.teachersupport.info.