Cheshire's ambulance service has the highest proportion of staff off sick in the NHS.
Analysis of official workforce data shows the North West Ambulance Service (NWAS) had an average sickness absence rate over the past two years of 6.9%.
So, on any given day, for every 100 people who work for NWAS seven are likely to be off work.
The average sickness absence across the NHS as a whole is 4.1%.
The figure for NWAS has fluctuated month by month but has consistently been at or near the top of the charts, rising as high as 9.2% in December 2014.
The most recent monthly figure for August 2015 was 5.8%, the lowest it has been since November 2013.
A NWAS spokesperson said the service is ‘very pleased’ that it has seen a ‘significant’ reduction in the number of ambulance staff off sick compared to last year and that levels are currently the best they have been for three years.
They said: “The physicality of the work undertaken by our ambulance service staff is very challenging; moving patients in very physically demanding scenarios, sometimes in very tough conditions and attending what can be traumatic incidents.
“The welfare of staff is something we take very seriously. Where staff are absent, many strands of support are offered both from the trust directly and from our occupational health services.
“The trust is constantly looking at its working environment and working practices to ensure it provides a safe and healthy working environment for all staff.”
Already in place are employment policies designed to assist the creation of a good work-life balance, such as the flexible working and sickness absence policies, and a health and wellbeing group which focuses on improving the working environment.
The spokesperson added: “NWAS does all it can to support staff and is continuously working to help them with all the challenges they face in their roles.”
Highest rates are in the North of England
The data, published by the Health and Social Care Information Centre, shows wide fluctuations in sickness absence rates across the NHS.
The analysis is based on an average of monthly sickness absence rates for each trust and clinical commissioning group between August 2013 and August 2015.
The areas with the highest rates tend to be in the North of England and the North West in particular.
After NWAS comes the Lancashire-based Calderstones Partnership NHS Foundation Trust, with an average sickness absence rate of 6.5%.
The North East Ambulance Service, the East Midlands Ambulance Service and Greater Manchester West Mental Health NHS Foundation Trust all had an average of 6.4%.