A quarter of employees start looking for a new job within two weeks of a bad appraisal, according to new research.
The survey, which examined appraisals on 500 employees, also found 40 per cent had begun a job search within a month.
Paul Jacobs, director of corporate communications at recruitment consultancy Office Angels, which commissioned the survey, said managers need to be aware of the pitfalls.
And he warned that clumsily handled appraisals could send valuable employees straight into the arms of competitors. "The time spent on the appraisal could mean the difference between motivating their staff or looking for a new candidate."
The research identified common mistakes made by managers, including continuously postponing the appraisal, rushing through it, and taking telephone calls during the meeting.
The research also found that a third of employees waited for up to a year at a time for feedback on how their career was progressing.
Russell Martin, global HR director at data services firm Primark, said there is a difference between a badly handled appraisal and a negative one that is fair.
"If you give someone a bad appraisal, then, in a good organisation, that should not be news to that individual. If someone is given a bad appraisal with continuous feedback, and wishes to leave, then to a certain extent that is a success for the organisation. You should be managing them out."
Primark spends considerable effort training line managers in how to carry out appraisals and give feedback.
P&O head office personnel manager, Ken Windsor, said: "Appraisals have to be done properly and that means with thought and care.
For example, I think a good appraisal will identify training needs. That makes it useful to both employer and employee."