I used to manage a shop for a large mult and I have heard just lately that a dispenser NVQ3 has been demoted due to making a serious error (not sure of the nature of the error) can this be done.
Well I'm sure anyone could be demoted as part of disciplinary proceedings.. It depends on the company policy I suppose? But I would imagine there must have been some kind of other trouble involved with the employee in question.. Maybe it was very serious but there was a reason to keep that person with the company (in other words they would have otherwise been dismissed).
Of course a company can discipline staff for poor performance.
Surely you don't think it right that a significant error rate should have no consequences?
We all make errors and disciplinary proceedings would depend on a number of factors eg frequency of errors, general aptitude and attitude, other issues etc. In general an error would be regarded as a learning exercise but if someone was harmed by it, that person/family would want to know what was being done to prevent it happening again. Removing an error prone individual from the opportunity to make any more errors would seem to me to be a sensible way to prevent further errors.