The overburdening of students with exams has been blamed on schools by the head of the official watchdog of the system.

Sir Williams Stubbs, chairman of the Qualifications and Curriculum Authority (QCA), agreed there was too much testing in England.

But that was not the fault of his organisation.

Sir William told BBC Radio 4's Today programme it was for the government to decide whether exams existed.

"What we are asked to do is ensure, when they do exist, they are competent and fair and there is an integrity about them."

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'Don't blame us'

"I think there is too much testing in schools, undoubtedly, but most of the testing is not done by national examinations," Sir William said.

"Most of the testing in schools is done by schools themselves practising with pupils.

Sir William: "Don't blame us"

"If they would reduce that, they would reduce much of the burden on pupils."

But the leader of the Secondary Heads Association, John Dunford, said there were too many external exams, putting "an unacceptable and counterproductive burden" on exam boards, schools, pupils and their parents.

"A new system of assessment must make better use of online assessment and must put more trust in the professionalism of teachers to use internal assessments," he said.

Sir William was commenting on the Department for Education's five-yearly review of the QCA.

It said there needed to be a sharper focus on the regulation of the big three exam boards, following a number of well-publicised errors.

But he said it was "a very useful stocktake" and "positive endorsement of our work to date".

The current education system leaves students over-examined, over-worked and over-pressured

Union leader Eamonn O'Kane

The Education Bill, currently going through Parliament, will give the QCA stronger powers to intervene with exam boards to get more effective management of exams.

Stronger powers

Sir William said this was something the QCA itself had requested.

A source within the QCA said it had a good working relationship with exam boards, but at present "we do see what they want us to see and hear what they want us to hear - we can't go in and tell them to open a filing cabinet."

Report whitewashes over the appalling debacle of examination board failures

Lib Dem Phil Willis

There has been an explosion in the number of exams sat last year and this, due to the Curriculum 2000 changes and the introduction of AS-levels.

The general secretary of the teachers' union the NASUWT, Eamonn O'Kane, said the government must tackle the cause of the problems.

"Telling the QCA to 'sort itself out' merely scratches at the surface of the symptoms," he said.

"The current education system leaves students over-examined, over-worked and over-pressured."

Schools' concerns 'ignored'

Exams at some point in a pupil's education were necessary, but there was "a crying need" for rationalisation of the whole system, he said.

His counterpart at the National Union of Teachers, Doug McAvoy, said the government had contributed to the "confusion and chaos" at the QCA by its erratic approach to the content of the national curriculum and examinations.

But the QCA was culpable in not having listened to schools' concerns over the assessment of pupils starting school, national curriculum testing and the lack of quality control of the exam boards.

"Nor has the QCA taken seriously its role in reducing the bureaucracy imposed on teachers," he said.

'Debacle'

The Liberal Democrat education spokesman, Phil Willis, said the report "whitewashes over the appalling debacle of examination board failures" which had left thousands feeling betrayed.

"The failure of the QCA to ensure appropriate monitoring systems has resulted in the British examination system losing its world class status," he said.

"The QCA's blind adherence to the limited focus of the government's curriculum has produced one of the most impoverished and inappropriate curriculums in the world."