Increasing numbers of support staff are having to do teachers’ work by delivering lessons, according to a survey by the Association of Teachers and Lecturers.

The union said more support staff were having to step up to “plug the gap” created by teacher shortages.

The ATL’s survey of almost 1,000 support staff members found that when acting as cover supervisors, 78 per cent feel the work they do is identical to that done by supply teachers.

This is up by 14 per cent on last year’s figure of 64 per cent.

While the role of a cover supervisor is to supervise pupils’ work but not teach, 72 per cent of respondents believe it is not possible to only supervise a class without delivering a lesson.

A higher-level teaching assistant in a secondary school in Durham said: “We are told sometimes with only five minutes or less notice that we are covering lessons.

“We are expected to teach students.”

More than a quarter (29 per cent) said they expected to fulfil the full range of a teacher’s duties even though they were paid at a support staff rate.

Support staff report that they are coming under pressure from heavy workloads, with 75 per cent saying they must work extra hours because their workload demands it.

Almost three quarters (73 per cent) said they were having to work extra hours for no extra pay.

A teaching assistant in a Bath primary school said: “I am very much expected to work extra hours and have been led to believe I would lose my job if I didn’t work extra without pay.”

Rising workloads may partly be the result of fewer colleagues, with 48 per cent of respondents reporting that their school had cut back on support staff.

Mary Bousted, the ATL’s general secretary, said: “Support staff are feeling the pressure to actually teach lessons and to plug the gap in staff shortages when teachers leave and do not get replaced.

“Support staff are struggling under excessive workloads as much as teachers and this survey shows that, sadly, support staff feel over-utilised and undervalued.”

State schools gained much greater freedom to use unqualified staff to teach because of a 2003 deal signed by the then-Labour government and most school staff unions, including the ATL.

The agreement aimed to reduce teacher workload by allowing schools to make greater use of support staff, for duties that could include teaching. Heads were allowed to use any member of staff they deemed suitable to teach, providing they were supervised by a qualified teacher.

But the supervising teacher did not have to be in the same room and the regulations would have permitted the extreme situation where the only qualified teacher in the school was the head.