More than two thirds of people are concerned about the amount of personal information held about them by companies, according to research by Ofcom.
Concerns about identity fraud and security surrounding personal details have also risen - by 15 per cent in two years - the regulator said.
However, more people who use the internet are now happy to give account details and other personal information online than in 2005, suggesting they are choosing websites more carefully, the report found.
Just 59 per cent of people are confident about telling whether a website is truthful or not. While the majority of people make a judgment about a website before entering details.