It's easy to forget that 9.5 million people – nearly 20% of the UK population – lack the basic online skills needed to send and receive email, use a search engine, browse the internet and complete online forms. The latest research shows that nearly three-quarters of adults who lack these basic online skills are vulnerable people, who are poor, have disabilities or are older.

Having digital skills is vital if we are to maximise economic growth and job creation. According to the 2012 Booz & Co report, The Case For Universal Digitisation, the lack of online skills is costing the UK economy £63bn in additional annual GDP growth. While online shopping saves the average consumer £560 a year.

The report also concludes that increased digital skills are of benefit to public services, leading to improvements in education; connecting older and isolated people to their communities more effectively; helping adults back into work and improving health and social services. These benefits make their greatest impact on the lives of the marginalised in society. And yet the latest figures from the Office for National Statistics show that 6.4 million people have never been online.

It's not just individuals who are losing out. Charities without an online presence are missing out on the £2.4bn now donated every year using the internet, over a third of all the annual charitable donations made in the UK. And central and local government could save more than £5bn a year if more services were provided online.

The UK is increasingly left behind due to an expanding digital skills gap: the European commission says 90% of jobs will require digital skills by 2015. Tackling digital exclusion is imperative. We want every individual, small business and charity to have the skills and confidence to benefit from the digital world.

Across the public sector, there's a tremendous opportunity to empower people and transform lives. At every point of interaction between government and the citizen we need to ask how to use this relationship to support and expand access to online skills. But it's not just a question of technology. We also need to ensure that people are able to safely communicate, shop, locate and share information, online. The government can't do this on its own – we need to work together to inspire people and organisations to share their digital skills with others – and build partnerships to roll out what works on the ground.

Digital exclusion is not an insurmountable problem. What's needed is investment in digital infrastructure, such as high-speed broadband, and a concerted campaign to promote internet usage. We need to make it easier for individuals and organisations to get online and navigate the internet.

For example, digital skills would make it much easier for someone to understand and manage a chronic health condition; for an unemployed person to find one of the many jobs that are now posted only online and for an elderly person to keep in contact with friends and family. Without these abilities, they risk being unable to manage their health, trapped in a cycle of long-term unemployment, or left to social exclusion and loneliness.

We have a unique opportunity and a moral imperative to work together to drive real change and build an inclusive digital society open to all.

• William Beveridge's welfare state was established to tackle five "giant evils" facing society. Over the next five weeks, the Guardian's Society Professionals section – a new space for people working in public services – will revisit the evils facing public services today: digital exclusion, inequality, chronic disease, underemployment and squalor. Join us to debate what society professionals can do to tackle them: theguardian.com/society-professionals