The number of Brits out of work and long-term sick has soared in the last two years - rising by 40,000 every month.
ONS figures show 2.3million “economically inactive” people were recorded as long-term sick in the three months to November 2021.
That is the highest since spring 2005 and up a quarter of a million on the same period two years earlier.
Of those, 1.8million say they do not want a job - up more than 300,000 in two years, and the highest figure ever recorded.
People who are long-term sick now account for 26.4% of all those who are “economically inactive”, the highest for two decades.
While the cause of people’s illnesses is not broken down, the numbers appear to have risen sharply during the Covid pandemic after hovering at around 2million since 2012.
Dr Kate Summers, an academic at the London School of Economics, suggested the rise was mainly driven by over-50s.
She said: "One explanation could be that Covid means people with a health condition who would previously have stayed in the labour market are not doing so, because of the possibility of becoming ill.
"Or they might have lost their job due to the pandemic and have not yet been able to find a new one."
Dr Rosa Morris, of the Commission on Social Security which campaigns for major overhauls to the benefits system, said two factors could include "Long Covid and increased mental ill health".
Commission Secretary Dr Michael Orton of the University of Warwick said it "will take some time" to know what caused the rise.
Labour condemned the figures, saying a “progress update” of the government’s Plan For Jobs makes no mention of the words ‘economic inactivity’, ‘sickness’ or ‘ill health’.
Shadow Work and Pensions Secretary Jon Ashworth said: "Ministers need to get a grip of this growing crisis in the workforce.
“They must fully explain what their plan is to fix the problems forcing more and more people out of the workforce - such as the ever lengthening waiting times for treatment which after years of running down the NHS now leaves many people out of work struggling with ill health.
“So far Ministers have no solutions. A credible plan for jobs would help people who can work find employment while offering true security to those who need it."
A DWP spokesperson said: “Our multi-billion pound Plan for Jobs is continuing to deliver, driving down unemployment and helping people to progress. We provide tailored support to those with long-term health conditions, to get them back into the workplace, and are committed to focusing on what people can do rather than what they cannot.
“Initiatives such as Access to Work and the Intensive Personalised Employment Support programme are helping support those with long-term health conditions into work and our recently-announced ‘Way to Work’ campaign will focus on getting job-ready people claiming Universal Credit into secure employment, rapidly filling vacancies which are at a record high.
“Meanwhile, for those who can’t work, we provide a strong welfare safety net.”
