The number of unqualified, trainee and foreign teachers has risen five-fold since Labour came to power, according to the Tories.
The figures from a parliamentary answer to a question from Michael Gove, the Conservative schools spokesman, mean headteachers are frequently filling vacancies with staff who are not qualified in the subject they are teaching.
There are now 16,710 teachers working in state schools in England without qualified teacher status (QTS), up from 2,940 in 1997.
The number of overseas trained teachers without QTS has also risen from 2,480 in 1997 to 10,970 in 2007. The figures will spark fears that children's education is being damaged.
Mr Gove said the figures showed that schools were not following official advice to only employ qualified teachers in state schools. "The Government's advice is that everyone should have the official qualification before teaching as a qualified teacher in a state school, so it is very surprising that the number without QTS has risen five-fold since 1997," he said.
"The huge increase in the number of teachers from abroad is partly due to the fact that so many British teachers are leaving the profession."
The figures do not include teachers from inside the European Economic Area (EEA) – which consists of all EU members plus Iceland, Liechtenstein and Norway – because their qualifications automatically receive QTS.
Last year, 1,562 teachers from the EEA were awarded QTS. Teachers from outside the EEA can work in British schools for four years before they have to obtain QTS.
A spokesman for the Department for Children, Schools and Families defended the Government's record on teacher recruitment, saying there were almost 40,000 more teachers in UK schools than in 1997, and that most overseas trained teachers were "excellently" qualified.
"We are clear schools should only employ teachers from overseas if they can demonstrate they have the skills, experience and qualifications relevant to the post."Reuse content