Two-thirds (65.6 per cent) of adults aged between 50 and 70 years old – known as Baby Boomers – have not done any moderate physical exercise lasting 30 minutes or longer in the past month, according to a report by England’s chief medical officer.

The 159-page document also found that from a sample size of 55,414, only 28 per cent performed at least four 30-minute moderate intensity sessions a month, equivalent to one a week.

National guidelines recommend adults take part in 150 minutes of moderate intensity, aerobic, physical activity per week.

By 2020, it is estimated that a third of British workers will be aged over 50.

The report, titled Baby Boomers: Fit for the Future, used figures from the Health and Safety Executive, Active People Survey and English Longitudinal Study of Ageing to produce its findings into the impact of lifestyle choices on the current and future health, mental health and sexual health of those born between 1945 and 1964.

Men were slightly more active than women, with 30 per cent of males taking part in four or more moderate physical activity sessions a month compared with 27 per cent of females.

There was also an age gradient within the Baby Boomer group. For men, 36 per cent of those aged 49–54 performed at least four 30-minute sessions a month compared with 27 per cent of those aged 65–69 years old.

A similar pattern was found for women, with 32 per cent of those aged 49–54 performing at least four 30-minute sessions a month compared with 25 per cent of those aged 65–69 years old.

The report also found regional differences, with the lowest rates of physical inactivity in the south. For example, 48 per cent of those living in London and 49 per cnet of people living in Richmond-upon-Thames were physically inactive compared with 81 per cent of those living in Gateshead and 80 per cent of people living in Stoke-on-Trent.

The report, which also looked at obesity and diet and nutrition, said that good-quality work is beneficial for Baby Boomers’ health, and that employers have a role to play by helping their staff to remain healthy enough to stay in employment.

Professor Dame Sally Davies, chief medical officer for England said: “People are living longer than ever and so retirement presents a real opportunity for Baby Boomers to be more active than ever before. For many people it is a chance to take on new challenges – it is certainly not the start of a slower pace of life it once was.

“Staying in work, volunteering or joining a community group can make sure people stay physically and mentally active for longer. The health benefits of this cannot be overestimated.”