Learner drivers may be unaware that a trainee instructor is teaching them, according to the AA.
The organisation said instructors at one major driving school were banned from telling learners that they were trainees.
When one learner driver noticed the trainee's pink badge they were told it meant the instructor was of a high quality.
Another trainee instructor was told to "make things up" if a learner asked about the badge.
In one case, a 17-year-old on her first-ever lesson was placed with a trainee instructor who, the learner said "was even more nervous than she was". A crash into a lamppost was only averted when the car stalled.
The AA said that up to 75,000 learners have in the last year been taught by an instructor they did not realise was a trainee.
A recent survey of 2,000 drivers aged 17-29 by research agency Research Now showed that only 2% of learners thought they had been taught by a trained person.
But the AA said that recent figures from the Driving Standards Agency showed that trainees made up more than 14% of all instructors.
An AA/Populus poll last autumn of 13,489 AA members showed that fewer than 0.5% would opt for a trainee instructor if given the choice.
© Press Association 2010