An extra 700,000 people of working-age will be living with major illnesses by 2040, experts have warned.

Analysis by the Health Foundation suggests 23% more working-age adults will be diagnosed with a major illness by 2040 – up from three million in 2019 to 3.7 million.

It is unclear how many of these people will be working at that point, will remain at work, might cut their hours due to illness, or may need to leave the workforce altogether.

The report said 80% of the projected increase in people diagnosed with major illnesses will be in the more deprived 50% of areas of England.

“Of the conditions that contribute most to health inequality, chronic pain, anxiety and depression and type 2 diabetes are projected to be the most prevalent in both the 10% most deprived and least deprived areas,” the report said.

“Population growth is higher in the most deprived areas in people aged 20 to 69 years and these conditions are more common in these age groups.

“For both these reasons, the number of cases is increasing fastest in the most deprived areas.”

Between 2019 and 2040, the Health Foundation projects that more than 270,000 more people will be living with chronic pain in deprived regions of England, alongside 240,000 more people with type 2 diabetes and 200,000 more people with anxiety and depression.

In the least deprived areas, there will be 140,000 more people diagnosed with chronic pain, 100,000 more with type 2 diabetes and around 60,000 more with anxiety and depression.

Jo Bibby, director of health at the Health Foundation, said: “Good health is our most precious asset, and a healthy workforce is the backbone of any thriving economy.

“We are already seeing the impact of poor health on the economy, with record numbers of people out of the workforce.

“Without action, the number of working-age people living with major illness is set to increase, particularly in the most deprived areas of the country.”

This is the second report from a research programme led by the Health Foundation’s Real Centre in partnership with the University of Liverpool.

The first report projected that the total number of people aged 20 and over (including pensioners) living with major illness would increase to 9.3 million in 2040, an increase of 2.6 million people from 2019.

The new report said people in the most deprived areas of England are likely to develop major illness a decade earlier than those in the least deprived areas.

They are also three times more likely to die by the age of 70.

The study warned that conditions such as diabetes, anxiety and chronic pain are often managed by GPs “underlining the need to invest in primary care and focus on prevention”.

The experts also said the Government’s target to improve healthy life expectancy by five years by 2035 and narrow the gap between the areas with the best and worst health will be missed by a “significant margin”.

Ann Raymond, economist at the Health Foundation’s Real Centre, said: “This report should be a wake-up call for politicians ahead of the General Election about the need for action to address rising ill health – our future health and prosperity as a nation depends on it.”

The report said that while action is needed in the NHS, more needs to be done to tackle issues such as smoking, poor diet, lack of exercise and drinking too much alcohol.

Saffron Cordery, deputy chief executive at NHS Providers said: “More support and funding for public health services is vital to ensure a healthier population. Prevention is better than cure.

“These findings are worrying but sadly not surprising given the cuts to public health and prevention services over the years.”

Latest figures show that the UK economic inactivity rate for those aged 16 to 64 was 22.2%. This is above estimates of a year ago and up in the latest quarter.

Economically inactive refers to the proportion of people of working age who are not in work and are not looking for work.

This can include students, people looking after family, those who have stopped work early or who are sick.

A Department of Health and Social Care spokesperson said: “Our Major Conditions Strategy will help with the management of conditions responsible for poor health and early death through proactive prevention, early diagnosis and aligning services to manage multiple conditions and health needs.

“NHS England is working to reduce health inequalities and improve the health outcomes of the poorest 20% of the population, regardless of where they live.

“Our Back to Work Plan, backed by £2.5 billion, is also helping more people into work – including those living with long-term health conditions – so everyone can reach their full potential.”