Workers are increasingly claiming stress or depression to avoid facing disciplinary action, a law firm has claimed.
Emw Law said it had become "almost the norm" for employees to get themselves signed off sick if their performance is questioned by a manager.
The Milton Keynes-based practice said the trend had become a "major headache" for employers and made disciplinary disputes difficult to resolve.
The firm's head of employment, Jon Taylor, said workers facing disciplinary action often accused a manager of bullying, forcing firms to spend time investigating the complaint.
"It is simply too easy for an employee to get his GP to issue a sick note. We are now seeing this happen in about three out of every five cases, compared with just a handful a few years ago."
Emw Law suggested that firms should consider getting a second medical opinion if they were not happy with a worker being signed off sick and said they should at least try to find out how long someone will be off work for.
"In many cases an independent doctor will actually advise that it would benefit the individual to get the issues resolved," added Mr Taylor.