The suspension follows investigations of malpractice and the closure of three of six Road Transport Industry Training Board assessment centres. The board is the biggest training agency of its kind with 16,000 youth trainees.
One centre remains closed pending results of a National Council for Vocational Qualifications inquiry. It is the first action since the council was given new assessment responsibilities last year.
Geoff Marshment, deputy chief executive of the RTITB, estimates that no more than a dozen candidates were affected. "If they were not passed properly then we will take appropriate action."