Ministers have promised tougher further education inspections following a report that says more than half of work-based learning needs significant improvement.
Schools inspectorate Ofsted, which will begin inspecting colleges next year, may be asked to lead a quality clampdown following the second annual report of the chief inspector of the Training Standards Council.
The report says that 55 per cent of work-based learning providers inspected this year were failing to monitor the quality of training. It says that assessment of competence at work - the backbone of national vocational qualifications programmes - was "in too many instances unreliable".
External checks carried out by awarding bodies were occasionally based on visits as seldom as once in five years. In such circumstances, the report says, "the awarding body could not have been well enough informed to make a reliable judgement about standards".
Inspectors found that often no attempt was made to take into account the learning and skills achieved by a student before they started a training programme.
Without this information, and in the absence of a fixed curriculum, which is not specified on NVQ programmes, trainees ended up taking the wrong courses, taking longer than necessary to achieve a qualification and going to work with unresolved numeracy and literacy problems.
Despite the fact that employers demand key skills - such as communication, teamwork and use of IT - very few training staff were qualified to help trainees acquire them. Inspectors found that 15 per cent of providers did not assess key skills and "some trainees and employers do not even know what key skills are".
Progress has been made, though, says the report. About 85 per cent of providers reinspected because of unsatisfactory grades last year were found to be at least satisfactory. But, it warns that "it is not enough to rely on intervention by the inspectorate" before improvements are made.
Ministers seized on the report as sufficient evidence to justify a quality clampdown when the new inspection regime for post-16 education and training, led by Ofsted, comes into force from April.
The system will cover private as well as public training providers. Lifelong learning minister Malcolm Wicks said that although there were some examples of outstanding providers, there was "still too much that is unsatisfactory, and a persistent residual element where training is poor".