Sir Tim Berners-Lee, the inventor of the World Wide Web, has said he is concerned about the impact of fake news, as he revealed plans to tackle "unethical" political advertising and the gathering of data.
The British computer scientist said - exactly 28 years after his world-changing invention - that three new trends have become alarming in the last year.
In an open letter published on Sunday, Sir Tim, 61, said that the misuse of data has created a "chilling effect" on free speech, and warned of democracy-corrupting "internet blind spots".
One issue, he said, was that most people find their information through a "handful" of sites and search engines, which are paid by clicks.
"The net result is that these sites show us content they think we'll click on - meaning that misinformation, or fake news, which is surprising, shocking, or designed to appeal to our biases, can spread like wildfire," he added.
"And through the use of data science and armies of bots, those with bad intentions can game the system to spread misinformation for financial or political gain."
He said that companies and governments are using mass data collection to "trample" on rights, leading to bloggers and dissenters being arrested and killed by repressive regimes.
"But even in countries where we believe governments have citizens' best interests at heart, watching everyone all the time is simply going too far," he wrote.
"It creates a chilling effect on free speech and stops the web from being used as a space to explore important topics, such as sensitive health issues, sexuality or religion."
Sir Tim also criticised political groups for using targeted advertising to tailor messages to voters.
"Targeted advertising allows a campaign to say completely different, possibly conflicting things to different groups. Is that democratic?" he said.
He urged for people to call for greater protection laws, and asked that Google and Facebook ramp up their efforts to tackle fake news.
The "internet blind spot" in political campaigning must be closed while alternative revenue streams are explored, so personal user data is not sold so indiscriminately, he said.
He plans for the We Foundation to work on the issues in a five-year plan.