According to the study conducted by management firm Firstcare, workers who went to their GP for a Fit Note were absent from work for 48 days on average, compared to 20 days for those who didn't apply for one.
Analysis of 22,086 employee records found that the majority of doctors are still locked into old habits and sign off employees for lengthy periods of time.
FirstCare said that GPs should be thinking about how a worker could return to the office earlier if their job is adapted or they are allowed to work fewer hours.
The government's new Fit Note system, which replaced the contentious sick note last April, was supposed to help reduce the £13bn sickness related benefits bill each year, but the figures appear to contradict the aims.
Speaking about the Fit Note system, James Arquette, a director at Firstcare, said it is "causing employees to be off work for longer without reducing the likelihood of repeated absence".
