More than 5,000 untrained teachers who have been allowed to work in academies and free schools under the Government's education reforms will be told they must gain a formal qualification or face the sack if Labour win the next general election.
Shadow education secretary Stephen Twigg said it was "unacceptable" that a Government which claimed to want to raise standards in the classroom let teachers who lacked the proper training work in state-funded schools.
"It is shocking that this Government is allowing unqualified teachers into the classroom," he told The Observer.
"High-quality teaching is the most important factor in improving education. We need to drive up the quality of teaching, not undermine it."
Under the first two years of a Labour government, unqualified teachers would be give access to training, but if at the end of that time they had still not qualified they would be out of a job.