Mr Blair killed off proposals from Sir Mike Tomlinson, the former head of Ofsted, for a new baccalaureate-style diploma after insisting that A levels had to be kept. But yesterday, during a visit to a secondary school in Enfield, North London, he told pupils that he believed that the so-called gold standard qualification was too limited as a form of learning and testing.

“The problem with A levels is that they are too narrow. I took English and French, and it would have been nice to have had an element of another language, some maths, some science,” Mr Blair said.

He went on to praise the International Baccalaureate, saying that it offered a “broader range of subjects” and meant that students did not specialise until they went to university.

Teachers’ leaders, who had been angered at the Prime Minister’s rejection of the Tomlinson reforms, were astonished. They said that the aim of replacing A levels with a diploma was to persuade more teenagers to study more broadly.

John Dunford, general secretary of the Secondary Heads Association, said: “If he feels that way, one has to ask why he turned down the best chance in a generation of broadening the education of A-level students by adopting the Tomlinson report. After the election, I and others will certainly want to explore with the Government how we can reinvigorate as much of the Tomlinson agenda as possible.”

David Hart, general secretary of the National Association of Head Teachers, said: “I am delighted the Prime Minister has suddenly expressed support for a baccalaureate because that is exactly what those of us who supported the Tomlinson reforms want to see.

“I think it demonstrates that there is some confusion at the heart of government because you can’t, on the one hand, support A levels in their present form and then, on the other, say we should be broadening the post-16 curriculum.”

Mr Blair’s criticism of A levels appeared at odds with Labour’s commitment in its manifesto to keep the exam. It has pledged to add an extended project to A levels and to include harder questions for bright students.

Sir Mike’s report last October, after a two-year inquiry, called for GCSEs and A levels to be phased out over a decade in favour of a diploma for students aged 14 to 19. It would have been set at four levels of difficulty, with students following individual “lines of learning” that allowed them to study a wider mix of subjects.

But on the day his recommendations for the biggest shake-up of examinations in

60 years were published, Mr Blair insisted that GCSEs and A levels would stay. His appointment of Ruth Kelly as Education Secretary in December was seen as a further signal that the plan was doomed.

In her response to the Tomlinson report in a White Paper in February, Ms Kelly promised to create 14 new vocational diplomas but insisted that GCSEs and A levels would continue, adding: “We won’t transform opportunities by abolishing what is good.”

Yesterday Mr Blair promised that every secondary school in England would get £75,000 for a new or refurbished science laboratory in the next three years. He said the £250 million plan would boost interest in science by ensuring that all schools had modern facilities.

“Today there are 86,000 more young people studying for first degrees in science and engineering than there were in 1997; the percentage of the total student body studying science and engineering has also gone up, and so too has the numbers studying for PhDs,” he said. “But we want these trends to develop further and faster, and our investment and reform in education will encourage this strongly.”

Funding for the initiative will come from the Department for Trade and Industry. Lord Sainsbury, the Science Minister, said that the money was needed because science facilities in one in three secondary schools were “appallingly out of date”.

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