One in 10 working-age people across Great Britain are claiming at least one health-related benefit according to new analysis which suggests someone aged 20 now is as likely to claim such a benefit as a 39-year-old was before the pandemic.

The Institute for Fiscal Studies (IFS) said the figure soared by one million since 2019, now accounting for 4.2 million working-age people (10.2%).

In the year before the pandemic hit, the figure was 3.2 million (7.9%).

The IFS, which published its findings on Friday following Rishi Sunak’s speech on major proposals for welfare, said the figure could be on course to pass five million people by 2028.

Using forecasts from the Office for Budget Responsibility (OBR) and the Scottish Fiscal Commission, the IFS said if things continue at their current pace, there could be 5.8 million working-age people on at least one health-related benefit by 2028–29.

If the pace slows but remains above the pre-pandemic norm the number of claimants is estimated at 5.4 million (12.4%), while if rates returned to their pre-pandemic levels, the IFS said the figure would be around 4.4 million recipients.

Spending on disability benefits and incapacity benefits for working-age people soared by £12.8 billion to £48.3 billion between 2019–20 and 2023–24, the IFS said.

This is forecast to rise to £63.7 billion by 2028–29, which analysts said is a £28.1 billion increase in the space of a decade.

Proportionally, the recent increase in claiming has been greater among younger people, the IFS said, with a 20-year-old now about as likely to claim a health-related benefit as a 39-year-old was in 2019.

For more than two thirds (69%) of new 25-year-old claimants, mental health and behavioural disorders were their primary condition, the IFS said, but this was the case for only around a fifth (22%) of new 55-year-old claimants.

The IFS said the causes of the recent rise in benefit claimants are “not yet well understood” but that it has “significant” implications for government spending.

Cutting benefits would be the most straightforward response, it said, but it added that this would see “significant losses for many vulnerable households” and would also fail to tackle underlying worsening health.

The rising cost of these benefits, and what might be done in response, will be a pressing concern for the next government and make the already tough fiscal situation harder still

Sam Ray-Chaudhuri, IFS research economist and report author, said: “A year or so ago, it seemed plausible that the rapid rise in numbers claiming health-related benefits was a transitory pandemic-related phenomenon. That explanation now appears unlikely, and today’s new forecasts reflect this fact.

“The rising cost of these benefits, and what might be done in response, will be a pressing concern for the next government and make the already tough fiscal situation harder still.

“Unfortunately, designing the right policy response is made much more difficult by the lack of clarity on what is fuelling the rise.”

The abrdn Financial Fairness Trust, which funded the IFS report, said while there are likely to be various reasons for the increase, much is still unknown in this area.

Its chief executive, Mubin Haq, said: “A range of factors is likely to be contributing to this rise, such as the pandemic, NHS waiting times and conditionality in the benefits system, but much remains unknown as to what is driving this growth.

“Cutting or reducing access to benefits would lead to severe hardship for millions with additional needs and fail to address the underlying conditions we now face.”

For the Conservatives to be attempting to make mental ill health another front for their culture wars is not just tone deaf, it's shameless and irresponsible

Labour’s shadow health and social care secretary, Wes Streeting, pledged his party will invest in mental health support, as he accused the Conservatives of “attempting to make mental ill health another front for their culture wars”.

He said: “We are experiencing an unprecedented crisis in mental health care, with children and young people crying out for support.

“For the Conservatives to be attempting to make mental ill health another front for their culture wars is not just tone deaf, it’s shameless and irresponsible.

“Instead of attempting to cover up the scale of the problem, the next Labour Government will give people the support they desperately need.

“We’ll roll out 8,500 mental health staff to cut waits, put mental health hubs in every community and support in every school, to help people back onto their feet.”

Delivering his speech on Friday, Mr Sunak said he believed in the “growing body of evidence that good work can actually improve mental and physical health” as he insisted there must be more ambition in efforts to help people back into work.

He called for more honesty about “the risk of over-medicalising the everyday challenges and worries of life”.