More than 200,000 people outside the workforce reported being affected by long Covid in the year to July, according to official figures that highlight the damage the pandemic has wrought on the jobs market.
The number of economically inactive people who say they suffer from the condition increased by 217,000 in the 12-month period, data from the Office for National Statistics (ONS) show.
It said this could partially explain why Britain’s labour force has shrunk so much since the pandemic began.
The UK is almost unique among rich developed countries in having a workforce that is smaller than before Covid, holding back economic growth as labour shortages push up inflation and limit activity.
Daniel Ayoubkhani, an analyst at the ONS, said: “Today's analysis shows that working-age people are less likely to participate in the labour market after developing long Covid symptoms than they were before being infected with coronavirus.
“[It] may therefore have contributed to the decreasing levels of participation seen in the UK labour market during the Coronavirus pandemic.”
It comes after the Government announced new measures to promote flexible working on Monday, giving employees the right to ask for part-time hours or homeworking from the first day of a new job.
The UK’s employment rate remains 1.1pc below its pre-pandemic level, making it an outlier among comparable countries. Half a million more people are out of the workforce because of long-term health issues.
The ONS’s research implies that a surge in people with self-reported long Covid has contributed to this, but experts said that there is still a large degree of uncertainty around what's causing the pool of workers to shrink.
In total, 23.3pc of people reporting a case of long Covid were inactive in July, compared with 21.4pc of those without.
The inactivity rate among long Covid-sufferers grew by 3.8 percentage points in the year to July, compared with just 0.4 points among other people.
This means an extra 217,000 inactive Britons said they were still dealing with long-term symptoms after contracting the virus in the year to July. Over the same period, the total figure of inactive people grew by 237,000.
There is at present no medical consensus on the nature of long Covid or what causes the condition. Reported symptoms range from extreme tiredness and depression to chest pains, diarrhoea and a high temperature.
David Finch, of the Health Foundation, said: “People with long Covid may be more likely to have poor health in the first place or be more likely to be economically inactive.”
He said that the number of inactive people was already edging up before the pandemic and that some of the increase came from the large generation of baby boomers ageing.
The rising state pension age could have previously masked some of this trend, he said, but the numbers were concerning nonetheless.
Mr Finch said: “Even if long Covid isn't the main reason for them becoming economically inactive, it will potentially be acting as a barrier to them going back into work.”
This sentiment was shared by Tom Waters, an economist at the Institute for Fiscal Studies.
He said: “I don't think that this is likely to explain very large quantities of the total increase in activity.
“As far as we can tell, most of the worsening in health is concentrated amongst people who were already out of the labour force.
“Instead, the decline in labour force participation is more related to early retirement.
While long Covid is more likely to lead to inactivity among older workers, the gap was largest for those aged 35 to 49.
Among this group, 19pc of long-Covid patients were inactive compared with only 12pc of people who did not suffer from it.
The ONS said the UK’s increasing levels of inactivity have not been seen in many other OECD countries despite long Covid having a global impact.
Indirect health effects of the pandemic and NHS backlogs may also be contributing to the shrinking workforce, they said but added that more research is needed.
New OECD analysis shows that coronavirus triggered a large drop in hospital activities in the UK, with non-urgent surgery down much more than in any EU country.