Further Education Funding Council inspectors criticised teaching at some institutions and pointed to poor quality checks in parts of the Japanese system.
But they pointed to the high level of investment in education by companies and students themselves.
The inspection team looked at four state-funded colleges and nine privately-run institutions as part of an overview of the Japanese training system.
Inspectors found vocational training standards were based on the reputation of individual institutions, and their success in getting students into work or other courses.
But they were largely unregulated, state inspections focusing instead on buildings and equipment.
Vocational training colleges were increasingly seen as a springboard to work for school-leavers and university graduates, the report said. But large companies often ran their own training organisations, and offered internal courses and examinations for staff.
Classes were large, at up to 80 students, with high-school graduates going on to vocational courses roughly set at the equivalent of A-level. Company training schemes were pitched slightly higher, but private colleges were doing work at GCSE level, with emphasis more on attendance than attainment.