The statistics watchdog has also questioned the rise in standards

Mary Bousted of the Association of Teachers and Lecturers said ministers had "grossly exaggerated" improvements.

Research commissioned by the union had found some rise in performance in the late 90s, but not as much as test data had suggested, she said in a lecture.

The Department for Education and Skills said standards in English and maths had never been higher.

It has recently also disputed a similar finding of overstated improvements, published by the government's own Statistics Commission.

'No comfort'

Dr Bousted, in a lecture at the British Library in London, was asking what education had to do "to rise to the challenge of the 21st Century".

Dr Bousted said ministers should trust teachers' assessments

She said her association had asked Prof Colin Richards of the University of Lancaster to consider whether standards were rising in English primary schools.

"Professor Richards' answer would give the politicians and the quango bureaucrats no comfort," she said.

One problem was that the levels children were expected to reach in national curriculum tests (the "Sats") were "arbitrary" but there was no official acknowledgement of this.

They could have been expressed differently; different people could have come up with different formulations.

And there was a "staggering" lack of published research on how the tests reflected the levels.

'Trust in teachers'

Prof Richards had stated "the most we can say about rises or falls in standards as measured by the Sats is that the evidence suggests that there was some rise in performance in the core subjects between 1995 and 2001 as measured by test results, but not as great as national test data (and the government) have suggested."

Dr Bousted said: "The changes we have seen to date are not statistically significant. Claims made about significant upward trends are grossly exaggerated.

"They cannot in any sense represent value for the millions of pounds from the public purse that have been spent on the national strategies and statutory assessments."

The money could have been much better invested in supporting teachers' assessments to improve attainment - the direction in which Wales, Scotland and Northern Ireland were travelling.

"Perhaps they have greater confidence and trust in their teachers," she added.

'Dramatic increase'

A Department for Education and Skills spokesman said: "Standards in English and maths in our primary schools have never been higher."

All the evidence - test results, international comparisons, and Ofsted reports - made this clear .

"Since 1997 the increase in standards and in the quality of teaching and learning in schools, has been dramatic and sustained.

"Last year 90,000 more pupils in English and 72,000 more pupils in mathematics reached the expected level for their age, than would have done in 1997."