Classroom assistants who cover lessons should be subject to the same rigorous inspections as teachers, the chief inspector has said.
David Bell said school inspectors should target classes being taken by teaching assistants to ensure lesson standards are not being compromised.
The move is part of a concerted drive to tighten accountability which will include greater pressure on coasting schools and put individual school departments under the spotlight.
The Government is also pressing for all failing schools to be closed within a year if they have not improved - a move opposed by Ofsted, which believes it will undermine its new light-touch inspection framework.
Teaching assistants are vital to the implementation of the Government's workforce agreement, which is supposed to give all teachers at least one half-day a week outside the classroom to mark and plan lessons from September.
Mr Bell told a teacher-training conference this week at De Montfort university, in Bedford: "The Government is never going to put enough money in for it (cover) to be achieved by more teachers. It is clear that teaching assistants are going to have to step into that role."
He said that inspectors would be instructed to sit in on lessons taken by assistants, as well as qualified teachers, and judge them equally. "If you give teachers a bit of non-contact time, then it is perfectly reasonable that non-teaching staff who are familiar and known to the children should stand in," he said. "But it is important that inspectors observe the quality of all teaching going on in schools - whether it is being done by qualified or non-qualified teachers. Ofsted inspects the teaching, not the teacher."
Bruni de la Motte, national education officer with Unison, which represents most support staff, said: "If the higher-level teaching assistants have been trained properly, they can do the job."Schools where assistants have not been would have a problem, he warned.
Andrea Studd, a classroom assistant who has worked at Enfield primary school, in Grimsby, for five years, said: "We are all observed in the course of our working lives and it would be reassuring for the schools, parents and for ourselves to know we had been judged as competent."
Unison said hundreds of schools were exploiting new higher-level teaching assistants, who are expected to provide the bulk of classroom cover, by only paying them more money for time actually spent in front of classes.
Union leaders say HLTAs, some being paid as little as 15p an hour for the extra work, should refuse to cover for teachers when schools make such ad hoc arrangements.
News 4, Leader 22