Colleges are reporting record drop-out rates, as only half of students on vocational training courses complete their qualifications.
The failure levels in higher education are revealed by the new 'success rate', a measure introduced by the Learning and Skills Council to measure students' progress.
The success rate shows how many students complete their courses, and how many qualify at the end. Only 43 per cent of those studying National Vocational Qualifications (NVQ) completed and passed their courses in England last year.
Patricia O'Brian, author of the report, said low level entry qualifications and a lack of motivation were most likely to cause students to drop out.
She blamed the Government's plans to get 50 per cent of students into higher education for forcing down entry qualifications.
Vocational training was a central driver in July's Government White Paper, 21st Century Skills - Realising Our Potential, which claims such training is essential to bridge the UK's skills gap.