The Government's new diplomas are being rushed into schools and risk being seen as the "poor relation" to traditional A-levels, a report has warned.
The diplomas, which will be taught to the first 40,000 teenagers from next year, are aimed at combining academic study with practical skills and work experience.
Ministers believe diplomas could replace A-levels as the major qualification for sixth-formers in the future but a report from the Oxford-based Nuffield Review cast doubt on the plan.
The review team warned that the diplomas, which will initially be in vocational subjects, could be seen by teachers as appropriate only for the less academic pupils.
A-levels and GCSEs will remain the more "prestigious" courses for the brightest teenagers, the review said.
Dr Ken Spours, from London's Institute of Education, said: "As long as A-levels remain unreformed, diplomas will end up being regarded as a poor relation."
The report said there was confusion about whether A-levels and GCSEs would be subsumed within the new diplomas or left as free-standing rival qualifications.
The Government rejected the idea that diplomas would suffer in the shadow of A-levels and GCSEs.
A spokeswoman for the Department for Children, Schools and Families said: "Diplomas will provide real opportunities for combining academic and practical options to allow every young person to make the most of their talents, whether they are going on to study, work, or an apprenticeship. They could well become the qualification of choice for young people.
"But because GCSEs and A-levels are long established and valued qualifications, that should not be decided by the Government, but rather by young people, schools and colleges."
