Nearly a quarter of the UK's adult population do not have the know-how necessary to successfully navigate the digital age, according to new research.
A survey by digital skills charity Go ON UK shows that 23% of UK adults do not have the 'basic digital skills' needed to complete online tasks such as safely carrying out transactions or avoiding malicious websites.
Baroness Martha Lane Fox, the internet entrepreneur and cross-bench peer who chairs the charity, said the lack of digital literacy was hurting the country.
Rachel Neaman, the charity's CEO, called it a "digital skills crisis".
"Digital competency is an essential skill for everyone and we believe that - without urgent action - the nation's lack of basic digital skills will continue to hold back economic growth, productivity and social mobility," Ms Neaman said.
The charity combined its research with other social factors - including education, income and health - to produced a map of the UK showing areas of the country seen as most at risk of digital exclusion.
The lowest levels of digital skills are in Wales, which has the UK's most limited internet access, and the Scottish Highlands, according to the results.
Ellen Helsper, an associate professor at the London School of Economics, who developed the methodology behind the map, called the findings a "wake-up call".
Go ON UK defines the five basic digital skills as managing information online, communicating, carry out transactions, finding solutions online and creating basic digital content such as social media posts.
While 89% of those surveyed could use a search engine, 27% could not buy or install an app.
The research also showed that while Scotland scores low overall in terms of digital infrastructure, it has the highest levels of basic digital skills of all the four UK nations.
And in Manchester, nearly 80% of adults have all five basic digital skills, but only one-third have used them in the past three months.
See the Go ON UK digital exclusion heatmap here.