"Successful completion rates are significantly lower for advanced GNVQs when compared with the BTEC Nationals and A-levels they are replacing," he said (see graphic). The staying-on rate had barely risen post-16. The system had "merely shuffled people between different routes."
The findings have been challenged by the National Council for Vocational Qualifications which insists that its own evidence of research and inspection suggests improved retention rates.
Mr Robinson accepts that his figures should be treated with some caution. "Students dropping out of GNVQs might otherwise have done A-levels or BTEC and found them too tough," he admits. But he said this did not account for the big differences in drop-out rates.
Also, while GNVQs were fast becoming the most popular form of vocational qualification for 16 to 19-year-olds, many still preferred traditional qualifications.
These, says Mr Robinson, "are particularly suited for part-time study to which GNVQs do not readily lend themselves." He predicts that traditional qualifications "are likely to retain a market share, offering a 'fourth route' for progression post-16".
Far from bringing greater clarity to the vocational qualifications, Mr Robinson believes GNVQs will increase the numbers and range available.
Coupled with the plethora of NVQs, many of which are taken by only a fraction of the workforce in some occupations, "these are adding to the qualifications jungle, not helping rationalise it as was intended.