As many as one in three adults in England could lack skills essential to finding work or carrying out basic everyday tasks, Joseph Rowntree Foundation claims.
The charity says 12.6 million would struggle to fill out an online job application form while a further five million cannot carry out one or more of a range of tasks including using a cash machine, writing a message or understanding household bills.
In many Western countries young people outperform their older counterparts, but the JRF says that in England older adults achieve higher literacy and numeracy scores than teenagers and those in their early 20s.
The charity analysed data gathered in 2011 and 2012 by the Department for Business, Innovation and Skills.
It found that 23 per cent of people aged 16-18 and 17 per cent of those aged 19-24 achieved the lowest score on the literacy skills scale used by the department.
The North East was among the worst faring regions in terms of both literacy and numeracy. It is also the region of England that consistently performs worst in terms of A-level and GCSE grades.
The charity said the figures painted a “troubling picture” of people being “let down” the education system or left behind in the modern economy.
The charity will next month publish a strategy aimed at eradicating poverty in the UK.
The organisation wants to see millions of pounds of additional government investment to ensure all adults meet basic skills requirements, including in IT, by 2030.
Its proposals include incentivising more adults to take night classes and encouraging employers to offer on-the-job training.
It also wants young people to be taught skills “grounded in the real world” such as financial planning and household budgeting.
Stephen Evans, deputy chief executive of the Learning and Work Institute, said: ‘’Everyone needs a set of basics for life and work in modern Britain. It’s shocking that so many people lack these core capabilities.”
A Department for Education spokesperson said: “Everyone, regardless of background or ability, should have the opportunity to reach their full potential.
“That’s why we have strengthened the national curriculum to ensure all children leave school having mastered the basics in literacy and mathematics early on. Alongside this our new gold standard qualifications and high quality apprenticeships will match the best education systems in the world and keep pace with universities’ and employers’ demands.
“To support lifelong learning and ensure we have a workforce with the skills to succeed we are investing £1.5bn in adult learning, have introduced tuition fee loans for part time students and published a dedicated skills plan so that more people gain the knowledge and skills to get on in life and help build a stronger country.”