Teachers have overwhelmingly rejected government proposals to let support staff take classes despite ministers' claims that it is the best way to cut workload, a new survey reveals.
Research commissioned by the National Union of Teachers found that four out of five teachers are against plans to allow support staff to cover for absent teachers and 60 per cent oppose assistants taking classes on their own in any circumstances.
The survey also reveals concerns about assistants taking on a greater teaching role even when a teacher is present. Almost two in five reject plans for a new grade of higher-level teaching assistants.
The findings have emerged as ministers were hoping to reach an agreement with the unions on cutting workload and "re-modelling" the profession.
Other parties involved in the talks have privately questioned whether the NUT is serving its members' best interests by opposing a proposal that could free them from the burden of covering for absence.
But despite pressure to reach agreement, the NUT continues to oppose the idea and will use the survey to support its position.
The findings will also increase pressure on leaders of the National Association of Schoolmasters Union of Women Teachers and Association of Teachers and Lecturers to join the NUT in publicly opposing the Government's plans.
Only one in 10 teachers says assistants should be allowed to cover for absent teachers and just one in seven agrees they should be able to lead classes without supervision.
Opposition was strongest among older and more experienced staff. "If Tony Blair turned up for an operation, would he let the porter operate?" asked one of those surveyed. Teachers also oppose assistants acting as pupil behaviour managers.
More than 31,000 teachers, all NUT members, took part in the survey, carried out by Sean Neill of Warwick university.
Teachers were strongly in favour of assistants continuing in their current role of assisting learning and providing administrative support. They also supported their use as sports coaches, language assistants, information technology technicians and music and drama specialists.
John Bangs, NUT head of education, said: "The survey shows that teachers have very clear ideas about the role of support staff. They are there to support not substitute for teachers."
But Christina McAnea of Unison, the public-sector union which represents assistants, accused the NUT of taking a "narrow-minded approach" and trying to pre-empt the outcome of talks. "They have asked loaded questions," she said.