Most people who are not online do so because they are not interested, according to the University of Oxford.
But a growing number have cited anxiety about widely-reported privacy issues, as well as a lack of knowledge on how to use the internet, as the reason for staying offline.
In 2013, when the last survey was carried out, only 1% of people questioned indicated that privacy worries were the reason they did not use the internet, but in 2019 that number had risen to 10%.
In 2013, 8% of people questioned said not knowing how to use the internet was the reason they did not use it, and in 2019 that figure had risen to 18%.
The number of those who did not use it because they had no interest in it fell from 82% in 2013 to 69% in 2019.
The lowest earners in the country remain the biggest group of non-users, with six in ten of those on an income of less than £12,500 using the internet, as well as older users whose usage declines sharply after the age of 50, the findings suggest.
Researchers, who spoke to about 2,000 people, are concerned that people not online are missing out on opportunities that could improve their quality of life.
“The majority of people are having positive experiences of internet use, regularly going online to watch their favourite shows or pay their utility bills,” said Dr Grant Blank, survey research fellow at Oxford Internet Institute, which conducted the survey.
“However, there is a widening perception gap between internet users and non-users, with non-users resolutely avoiding the internet.
“Often these non-users are from low-income groups, where being online could potentially improve their quality of life.
“There’s an interesting paradox here, with internet users being less likely to take action to protect their privacy, while non-users tend to be put off by privacy concerns.
“These concerns could perpetuate the digital divide, with many people missing out on the benefits of the internet, such as access to health information, employment opportunities and reduced prices online.
“There is a real opportunity to engage with non-users to address their concerns and help them understand the opportunities the internet can bring.
“We hope this survey contributes to the public debate about what further steps can be taken to narrow the digital divide.”
Despite active internet surfers reporting positive outcomes, almost 70% said they were uncomfortable with targeted advertising and tracking data used by tech giants.
“Helping motivate people who lack confidence to get online is essential to bridge the digital divide,” said Andy Wales, chief digital impact and sustainability officer at BT, which co-sponsored the study with Google and the Department for Digital, Culture, Media and Sport.