Further education college chiefs have warned that a rigid grading system adopted for the new "vocational A level" may send failure rates soaring.
College heads have already reported worryingly low scores among the first batch of students to take modules for the advanced vocational certificate of education, introduced as a replacement for the advanced GNVQ last September.
A survey by the Association of Colleges revealed that on some AVCE courses, only one in ten students passed the first modules taken in January.
Course leaders complained that students were being asked to cope with standards equivalent to A level in the first year of the new programme.
The AoC fears that the next set of results, due in September following further modules taken in the summer, will show that the AVCE's grading system is making passing vocational A levels even harder.
Unlike traditional A levels and AS levels, the grades achieved by AVCE students are not adjusted to take account of the performance of students in previous years.
This means that even if an entire cohort of AVCE students does badly, there will be no adjustment to the grades they are awarded.
Judith Norrington, the AoC's director of curriculum and quality, said this left AVCE students at a disadvantage compared with those taking traditional A levels.
She said: "Even though this is the first year for the AVCE, that does not mean that the results can't be adjusted in the light of the performance of previous advanced GNVQ students.
"My concern is that students should be judged fairly and equally, whatever route of study they choose. By having a different grading system for the AVCE, it means there is no safety net for those students if something is wrong with the qualification."