Bad behaviour in classrooms and too much government red tape is prompting a growing number of school teachers to quit, the Conservatives said on Thursday.
They said over a quarter of a million qualified teachers under 60 are not teaching.
Nearly 100,000 left the profession between 2000 and 2005, more than double the number that left in the preceding five years, according to Tory figures.
Shadow Children's Secretary Michael Gove added in a statement: "Not only are our children not achieving as they should, talented teachers are not where they should be - in the classroom, opening young minds to new horizons.
"With more than quarter of a million gifted professionals no longer in teaching we have to ask why they've given up on education under Labour.
"I fear that a combination of classroom bureaucracy, government micromanagement and poor discipline in too many schools has encouraged a drift away from teaching."
The Conservatives also said more teachers are retiring early, the number rising to 16,850 in the past year from 8,500 in 1999.
More full-time teachers, too, are going part-time, they added.
Schools Minister Jim Knight dismissed the claims.
"Recruitment into the profession has never been more buoyant, and teaching is now the career of choice for many highly qualified, talented individuals," he said.
"Indeed Ofsted has said this is the best generation of teachers ever."
