Dr Nicholas Tate says GCSEs are a barrier to young people's progress, with revision, mocks and exams effectively taking a year out of education for students who will go on to take higher qualifications. He says that the exam also further alienates those who are already disaffected and under-achieving.
The chief executive of the School Curriculum and Assessment Authority told The TES the exam could be scrapped in favour of a system of credits which students could accumulate on their way to formal qualifications at 18.
"There might be other ways of recognising attainment at 16 for people, most of whom will continue in formal education and training," he said.
"Very radically, we could think - as quite a few countries have done - of dispensing with external examinations at that age. Certainly, GCSE is enormously costly."
Dr Tate has already floated the idea of a system of credits in core skills which could be accumulated throughout secondary, further, higher and adult education as well as in work or training.
His comments are thought to be the first public expression of doubt over the effectiveness of GCSE by such an influential policy-maker. They follow growing private concern that the exam and the sheer number of compulsory subjects at key stage 4 could impede some students' progress.
Current 14-16 initiatives, including vocational qualifications and closer links to colleges and the workplace, had potential, but there was a case for more radical measures, says Dr Tate.
One option could be to end the national curriculum at 14. Alternatively, some schools could be allowed to drop the national curriculum at key stage 4 in an attempt to remotivate students.
"For many young people GCSE is motivating - it has proved a successful qualification. But to a very substantial minority, it makes things worse and a more flexible curriculum less dominated by formal qualifications may be the way forward," he said.
But he acknowledged the risk that a separate curriculum for some young people could leave those students branded "second-class".
GCSE will not form a part of the national curriculum review which is due to begin next spring with any changes implemented in September 2000. But the review's outcome could make changes to the exam inevitable. Changes would be introduced in 2002.
Dr Tate argues Britain is unique in having such formal examinations at both 16 and 18. That is partly a result of post-16 specialisation and support is growing to replace A-levels with wider, baccalaureate-style courses.
Dr Tate's ideas were floated at a national conference of youth workers in Manchester on Monday where he recognised the role youth services played in offering non-mainstream paths into education and training.
Research by Keele University has shown the large numbers of secondary school pupils who are turned off by school - up to 40 per cent said they would rather not go.
Dr Tate urged the Government to emphasise personal, social, civic and moral education in the curriculum to help instil a sense of community and civic responsibility in young people.
And he called for an expansion of post-16 community service schemes and for young people to be more involved in the running of their school if they were to become engaged again in the political life of the country.