Sick leave costs the economy 175 million working days – equivalent to £13.4 billion a year - and employers believe that 12% of absences are faked, according to research by the CBI and AXA.

The research revealed that the average worker takes seven days a year off sick and long-term absence of 20 days or more accounts for 43% of all working time lost, costing £5.8bn. In the public sector 52% of absence is long-term, while in the private sector the figure is 38%.

According to the survey, companies that offer rehabilitation programmes and flexible working can help employees back to work and lose less time to absence.

Short-term absences are a key concern. The great majority of absences are genuine, but employers believe around 12% are suspect and involve staff “pulling a sickie”. That means 21 million days were lost in 2006 at a cost to the economy £1.6bn.

Asked to cite the reasons behind fake illness claims, 70% of employers felt staff are inclined to create unauthorised long weekends by taking Mondays or Fridays off sick, while 68% said there is a link between sickies and holidays, and 39% said absence is linked to special events, such as major sporting tournaments.

Looking at all absences, the 2006 research shows an increase on 2005, when the average employee took 6.6 days off sick, and the total number of days lost was 164 million.

The best performing organisations lost only 2.7 days per employee, while the worst lost 12. The public sector had the highest average absence at nine days per employee, up half a day from 2005, while the private sector lost 6.3 days. Despite the governmentÕs efforts, public sector absence was 44 per cent higher than in the private sector.

Susan Anderson, CBI director of human resources policy, said: “The gap between organisations with the highest and lowest absences is over nine days, and clearly some are managing absence better than others. In particular, if the public sector could match average private sector absence levels, then the taxpayer would save £1.1bn a year - enough to build seven new general hospitals.”

The most important factor that influences absence is organisational size. In 2006 employers with fewer than 50 staff had just four days of absence per employee, but this doubled to eight days in organisations with over 5,000 employees.

Organisations that recognised trade unions experienced more absence - eight days compared to 5.6 days in non-unionised workplaces. This correlation was found regardless of size or sector, except in firms with less than 50 employees.

The top causes of absence are colds and flu with back pain in second place. For long-term absence, non-work related mental ill health - including stress, anxiety and depression - was the most significant cause of absence among non-manual staff. For manual staff, back pain topped the list.