Teaching assistants are increasingly having to lead lessons and manage classes by themselves amid ongoing teacher shortages, according to a study.

Union Unison said pupils were missing out on essential support because low-paid teaching assistants increasingly provide cover for absent teachers.

Its report, Teaching on the Cheap?, is based on a survey of almost 6,000 teaching assistants in England and Wales, which found that almost half said they are covering more classes now than they were a year ago.

​Unison said too many low-paid teaching assistants end up performing roles for which they are neither trained nor paid, claiming that pupils are being taught “on the cheap”.

​Covering for teaching colleagues means teaching assistants’ normal tasks are not being done, leaving pupils they support without any assistance, said Unison.

​Teaching assistants described regularly being told to lead classes ranging from nursery to year six, with just minutes to spare.

​Those working in secondary schools reported planning and teaching subjects at GCSE level where teachers have left and not been replaced, said Unison.

​The union called for a review of the role of teaching assistants, saying they are now providing cover in circumstances “way beyond” what has been nationally agreed.

​Unison’s head of education Mike Short said: “The strain imposed on teaching assistants is both unacceptable and exploitative.

“When they’re leading full classes, teaching assistants are being diverted from what they do best and pupils who need additional support are missing out.

​”Schools’ budgets are so tight that, instead of getting in supply teachers to cover classes, heads are having to use teaching assistants on the cheap.

“Ministers are entirely responsible for the funding crisis that’s putting schools in this impossible position.

​“Many children can’t grasp the basics without the critical assistance of teaching assistants. Redeploying them to other roles is unfair on everyone.

“Parents will rightly assume their children are being taught by teachers, not teaching assistants.”

Paul Whiteman, general secretary of the school leaders’ union the NAHT, said: “This is symptomatic of the recruitment and retention crisis that this Government has overseen in our schools.

“It is not right that teaching assistants should be asked to routinely cover classes but sadly sometimes schools have literally no other choice.

“Teaching assistants play a crucial role in our schools, particularly for pupils with additional needs, but we should not expect them to fulfil the role of the teacher.

“The only way to properly address this is for the Government to tackle the recruitment and retention crisis so there is a sufficient supply of teachers for all subjects, across all parts of the country.”