A fifth of trainee teachers are failing compulsory computerised tests for literacy and numeracy the first time they sit them.
Figures published by the Training and Development Agency for Schools (TDA) have alarmed conservative commentators.
But the agency insists that the figures have been misrepresented because it does not take into account re-takes or the fact that trainees are not allowed to join the profession until they pass.
The 45 minute on-screen tests in numeracy, literacy and ICT have been compulsory since 2001 and can now be taken online. Statistics for the 33,000 trainees who sat the tests in 2004-05 show that, on their first attempt, 81 per cent passed maths, 79 per cent English and 75 per cent computing.
The Daily Mail reported this week that the results proved the "alarmingly low standard of new teachers" which would have a "devastating long-term effect on the youngsters they teach".
Chris Woodhead, former chief inspector of schools, told the Mail: "The tests are hardly more difficult than those sat by 11-year-olds. It's extremely worrying if a teacher can't spell and add up because the children are never going to learn."
However, the TDA pointed out that teachers were not allowed to qualify until they passed the three tests, which they can only retake a maximum of three times.
If those who passed at their second attempt were included, there was an average pass rate of 92 per cent. A TDA spokesman said that the skills tests were one of 42 standards trainees needed to meet.
"So nobody teaches in a state school without passing them," he said. "They are a central part of a highly rated training regime that has led Ofsted to judge that the current generation of new teachers are the best ever."
Teachers are also unable to begin their training without the equivalent of a C grade or above at English and maths GCSE.
The National Union of Teachers has criticised the tests since their introduction. "We have always seen them as an unnecessary burden on trainee teachers," a spokeswoman said.
"The poor way some of the questions are phrased would challenge the brightest of us, let alone someone who is nervous. What does a fine arts teacher need to know about maths anyway?"