Birmingham's head of education has cast doubt on the ability of GCSEs in English and maths to assess the literacy and numeracy skills of the nation's young.
Tony Howell called for a "national debate" on whether the exams were still a relevant measure of what teenagers needed to know to get on in life.
Mr Howell also said it was time to reconsider if they should remain compulsory and should instead be replaced by a test that assessed "functional competence" in the core subjects.
His outspoken comments places Europe's biggest education authority in direct conflict with the Government, which has put increased emphasis on achievement in GCSE English and maths.
Prime Minister Gordon Brown recently said he wants to ensure no school has less than 30 per cent of pupils getting five or more good GCSEs, including English and maths.
Based on that measure, more than a third of Birmingham's secondary schools would have failed to meet the target this year.
Mr Howell said: "There is a need for a national debate on the level of literacy and numeracy that everyone needs. In many ways the way we test in these subjects is more relevant to the 19th century grammar school system.
"I would like there to be a national standard in functional literacy and numeracy to be achieved. Once you get to GCSE level, it starts to go into much more academic aspects in English, including the cannon of English literature.
"That is important, but to pretend the other side isn't is to miss a trick."
Mr Howell added: "Unless we have something that says you have reached the functional literacy stage and you are going on now into the GCSE stage, we end up pushing too many children into that without making sure they have the fundamentals right."
Mr Howell said feedback from employers and universities suggested practical literacy and numeracy skills were lacking in GCSE pupils.
"We have to ask what do we mean by literacy and numeracy. Part of the challenge is what is the nature of the exam at Key Stage four.
"I have tried to push the Government to say 'lets have a national debate on what literacy and numeracy means'."
Based on current Government focus, pupils who do not get a GCSE graded between A* and C at GCSE are judged to have failed to get the required level of competence.
But Birmingham City Council claimed this was unfair, as more than 90 per cent reached Level One (a pass graded between D and G) which indicated basic competence.
The authority's elected head of education Councillor Les Lawrence questioned the Government's obsession with such targets.
"I sometimes worry that national politicians of whatever party in their intent to raise the level of attainment on behalf of young people can often inadvertently create an environment which is threatening."
Birmingham reported a three per cent increase in attainment this year to 62 per cent of 16-year-olds hitting the five or more GCSEs graded between A* and C.
The pass rate is better than every other major urban authority in the country and above the national average of 60.3 per cent.
The improvement rate represents an average annual rise of 3.3 per cent annually over the last six years.
But if A* to C passes in maths and English are factored in, the authority's pass rate slumps to 41.8 per cent.
Education chiefs believe new vocational diplomas which are currently being phased in will address this because they place a greater focus on functional numeracy and literacy.