Employers suspect that one in eight worker-absences last year were examples of staff "pulling a sickie", meaning 21 million days were lost.
The Confederation of British Industry (CBI) says these unauthorised absences cost the British economy £1.6 billion in 2006, warning that a "culture of absenteeism" is seeping into UK workplaces.
In total the trade association claims its survey shows that 175 million working days were lost to illness over the last 12 months, with long-term absence of 20 days or more accounting for almost half of lost time.
This means that according to the CBI the average worker took seven days off work sick in 2006, a rise of six per cent on the previous year.
But responding to the survey's claim that short-term absence is a "key concern" for companies, the TUC's general secretary Brendan Barber said that workers' absences were being aggravated by "unsympathetic managers".
The CBI's research goes on to claim that almost three-quarters of employees created four-day weekends by feigning illness on Mondays and Fridays in 2006.
Susan Anderson, director of human resources policy at the trade association, said: "We've all just enjoyed the four day Easter weekend, but some people think they have a right to use 'sickies' to take long weekends or extend holidays as they please.
"Unauthorised absence puts colleagues under unfair pressure, and loses employers and taxpayers well over a billion pounds."
But countering Mr Barber's claim over uncaring managers, Ms Anderson insisted that "employers understand that most absence is genuine".
"It is in nobody's interest if staff come to work when they are not well," she concluded.