Classroom support staff across the UK say they are increasingly being asked to carry out roles that have traditionally been restricted to those in teaching jobs.

Research by the Association of Teachers and Lecturers (ATL) shows that a third of support staff in UK state schools conducted lessons for absent teachers, while more than one-fifth (22 per cent) said this was a growing trend, with this group being responsible for more classes in 2012-13 than in 2011-12.

The ATL results were compiled from polling 1,400 of its members who work as classroom support staff in state schools in England, Wales and Northern Ireland.

Existing rules state that classroom staff who do not have full qualified teacher status are allowed to teach small groups of children when under the supervision of a fully qualified educator, but they should not be teaching entire classes and preparing lessons.

One of the higher-level teaching assistants from a secondary school in England who took part in the survey told the union that they prepare, teach and mark at least four lessons for two year 7 classes and a year 8 class. They described it as getting teaching on the cheap.

ATL general secretary Dr Mary Bousted said: "Schools are selling children short by using teaching assistants to teach classes when the regular teacher is unavailable.

"We are totally opposed to this exploitation of support staff who are being used as a cheap option to teachers."

A Department for Education spokeswoman responded to the research by saying underqualified staff should not be responsible for teaching.

She explained that teaching assistants and other classroom support staff play a vital role in education and it is up to all state school leaders to ensure taxpayers get value for money, but the government's rules are clear.

As someone who is looking for a teaching job, what do you think about underqualified people being paid less to do a job that you have been working hard to prepare yourself for?