Data from the Office for National Statistics (ONS) showed an increase in economic inactivity since the start of the pandemic, caused in part by people with long-term illnesses.
An additional 150,000 were classified as long-term sick between May and July 2022, while the total figure has increased by more than 240,000 compared with the same time period last year.
Nearly 400,000 workers have left the job market due to health issues since February 2020.
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Charlie Thompson, employment lawyer at law firm Stewarts, said employers are responsible for managing their workers with long-term health problems.
He told HR magazine: "There is a significant number of 'walking wounded' who are employed but on intermittent sick leave, on long-term leave or on the brink of a breakdown. Employers have a duty of care to their staff, and where they cause a breakdown or exacerbate an existing condition, they may be liable.
"Increased homeworking presents challenges; with increasingly blurred boundaries, more and more people are not just working from home, but living at work. And although an employee is working from home means that an employer may be less aware of what is going on, it does not reduce an employer’s legal responsibility."
The increase in long-term sick workers contributed to a fall in unemployment between May and July 2022, from 3.8% to 3.6%.
Zofia Bajorek, senior research fellow at the Institute for Employment Studies (IES), highlighted the resources available to HR teams to help sick workers.
Speaking to HR magazine, she said: “With the number of people classified as long-term sick increasing, employers and employees may be looking at their HR departments to see what support can be given to employees who may be working with a long-term condition.
"Occupational health will be able to provide expert advice for how employers can introduce workplace adjustments, that can aid employees to stay and thrive in the workforce. Wellbeing action plans and wellbeing passports are all interventions that can help employees with both mental and physical conditions communicate what the workplace can do to help them."
Bajorek added that wellbeing should be a top priority for HR teams.
She said: "These statistics highlight the importance for organisations to focus on the wellbeing agenda, and to focus on capacity and not incapacity – to design work to focus on what employees are able to accomplish and help them thrive at work.
"This may require HR managers and employers to engage in wellbeing audits and workforce planning exercises to ensure that work is fairly distributed, and extra work is not placed on remaining employees, adding to potential stress."
