Christina Barratt was used to the 12- to 14-hour days. For years, she would get into her car each morning and set out to department stores and other retailers all over northwest England, selling greeting cards for a large manufacturer.

“It’s a very demanding, busy job,” she said, recalling how she had to make sales, manage client accounts and grow the business, while often travelling long distances.

In March 2020, at the age of 50, Barratt got Covid. She hasn’t been able to work since.

Barratt is among 3.5 million people — or about one in 12 working-age adults in Britain — who have long-term health conditions and are not working or looking for work. The number ballooned during the first two years of the pandemic when more than half a million more people reported they were long-term sick, with physical and mental health conditions, according to an analysis by economists at the Bank of England. The sharp rise in ill health is a startling problem itself, but there has also been a growing awareness in Britain about the negative effects on the economy of having so many people unable to work.

Sickness is adding to the growing sense of malaise in a country troubled by high inflation and the economic costs of Brexit, where the National Health Service is overwhelmed and workers across industries are striking in ever larger numbers, coming after a year of severe political upheaval. With the unemployment rate near its lowest point in half a century, businesses have loudly complained that they have been unable to hire enough workers, leaving the government grappling with how to expand the labour market.

Before the pandemic, a growing labour market had been “the single cylinder of growth in the economic engine”, Andy Haldane, the former chief economist of the Bank of England, said in November during a lecture at the Health Foundation, a nonprofit organisation. It “has now gone into reverse gear.”

Britain is in “a situation where for the first time, probably since the Industrial Revolution, where health and well-being are in retreat” and acting as a brake on economic growth, said Haldane, who currently serves as the chief executive of the Royal Society of Arts, an organization in London that seeks practical solutions to social issues.

The economy is probably already in a recession, according to forecasts by the Bank of England and others, and is expected to return to only meagre growth in 2024. Some economists have warned that shortages of workers could deepen the cost-of-living crisis if it causes employers to raise wages to attract workers in a way that threatens to entrench high inflation into the economy. That could prompt the central bank to keep interest rates high, pushing up borrowing costs and restraining the economy.

At the heart of the problem is a high economic inactivity rate that has barely budged despite the end of pandemic lockdowns, a boom in labour demand and a high cost of living. As of October, over half a million more people were counted as inactive than before the pandemic, according to the Office for National Statistics. In a separate study looking at data for the first two years of the pandemic, Jonathan Haskel and Josh Martin, economists at the Bank of England, found that nearly 90 per cent of the increase in economic inactivity could be attributed to people who were long-term sick.

The extent to which sickness is forcing people to leave the workforce is still being debated among researchers in Britain because the reasons for not working can change over time. But there is little disagreement that the economy is being held back by having so many people who say ill health has kept them from working.