"In order to be able to turn the whole thing off or really block, suppress one particular idea then the countries and governments would have to get together and agree and co-ordinate and turn it from a decentralised system to being a centralised system.
"And if that does happen it is really important that everybody fights against that sort of direction."
Sweden has topped the Web Index league table launched by the World Wide Web Foundation, followed by the US in second and the UK in third.
Nepal, Cameroon and Mali were the bottom three of 61 countries measured using indicators such as the political, economic and social impact of the web, connectivity and use.
Asked about rumours that he himself was one a handful of people who had the ability to switch off the net, Sir Tim joked: "I am afraid that now that you know I will have to shoot you.
"I have put on filters which allow me just to investigate just every single word that any of you have said to each other.
"You won't know what is happening, but as you talk to each other it will be quietly modified to appear to be whatever I want you to be saying.
"I will take a deep control of the world.
"Apart from that, everything will remain as usual."
Comedian and avid Twitter user Stephen Fry, 55, was also present at the launch of the Web Index at the National Theatre in central London.
Fry was supposed to be introducing the panellists speaking at the event, but arrived late and blamed it on a visit to a nightclub the night before.
Speaking afterwards, he said the greatest threat to freedom on the internet was the attempt to curb the free exchange of ideas.
He said: "The free exchange of ideas is what is behind democracy or any kind of open way of living and when you control the press, when you control television, radio or now what you might call the web, all the transactions of knowledge that flow between people, individuals and countries, when firewalls are put around that, when information is not allowed in or out of a country, it is pretty much inexcusable."
- AAP