The Assembly's own audit committee found that standards among Wales's 121 work-based training providers presented "unacceptable risks to public funds". Also, under a system inherited from the former post-16 funding body ELWa, work-based learning providers have been overpaid by pound;4.6 million.
Problems are said to have arisen from an over-complex data collection mechanism. But it was also found that some overpayment stemmed from the failure to report students who had dropped out or finished training.
Steve Marshall, director of the Department of Education, Lifelong Learning and Skills, is to submit a paper to the Assembly's senior business team, setting out lessons learnt.
It will say that all third-party providers must have compulsory training for new projects or initiatives.
According to an Assembly government spokesperson, "robust mechanisms" have been designed to strengthen financial systems and controls.
Minimum standards will apply to all providers. Systems will be graded simply as acceptable or unacceptable.
The audit committee was also concerned by "relatively poor learner attainment levels" and concluded that these were linked to inadequate financial controls. The Assembly says that expected standards should be made clear and that firm probation arrangements will be laid out to deal with early evidence of problems.
It will also be introducing a performance improvement programme, as well as funding trainer-led projects aimed at raising post-16 standards.