Managers and senior officials work the longest total hours of any major occupational group, but much of it is unpaid overtime, a new report by the Office for National Statistics on hours worked has shown.

By comparing data from the Annual Survey of Hours and Earnings, which looks at paid hours, and the Labour Force Survey (LFS), which collects total hours worked, it is possible to draw inferences about which groups are likely to work more hours than they are paid for.

This analysis shows that full-time managers and senior officials work 38.5 paid hours a week, but actually work 46.2 hours, a difference of 7.6 hours. Likewise, professionals work 36.6 paid hours and 43.4 total hours (a gap of 6.8 hours). By contrast, process, plant and machine operatives and workers in elementary occupations, regarded as the lowest skilled jobs, work paid hours of 44.2 and 41.4 hours respectively, but have little gap between paid and total hours.

LFS data show that in April-June 2011 average working time for all in employment stood at 36.3 hours a week, a fall of 4.7% on the 1992 level of 38.1 hours a week. This has been affected by changes in the structure of the economy, with a higher proportion of employment being in services where hours tend to be shortest (35.0 a week in 2011 compared with 41.2 for both manufacturing and construction). However, the increase in part-time working (up from 24% of all in employment in 1992 to 27% in 2011) has also affected average hours.