One of Google’s most senior executives issued a stark warning tonight that the power of the internet to free some of the world’s most oppressed people risks being overturned by autocratic governments who seek to “Balkanise” the web by controlling what can be accessed.

Eric Schmidt, the current executive chairman of the Silicon Valley internet giant, said technology had the potential to be a “great leveller” which would empower the poor like never before. But he added that dictatorial regimes were increasingly looking to control who has access to the web by “filtering information they fear or prohibit.”

The 57-year-old software engineer, who stepped down as Google’s CEO last year after more than a decade in the driving seat, called on the international community to “fight for the future of the web” stating that at least 40 governments are now known to engage in online censorship compared to just four a decade ago.

“Last year we saw in Egypt what happened when a government tried to turn the Internet off, “ he said last night in a speech at the Science Museum in Kensington, referencing the moment when the struggling regime of Hosni Mubarak tried to block the web in the face of mass street protests. “Now many governments are attempting to build their own walled Internet, a Balkanised web in which you and I do not see the same information and no one knows what has been censored.”

Using somewhat apocalyptic language, he stated that web users “face the real possibility we could end up living in society in which software silently deletes our voices, our thoughts our culture.”

“Make no mistake, he added. ”This is a fight for the future of the web and there is no room for complacency.”

Mr Schmidt’s comments came in a speech that outlined his belief in how the internet will develop over the coming decades. He painted a utopian portrait of a world increasingly liberated by technology, where the growing affordability of smart phones and web connections would help the world’s poorest join the information super highway and fight their would-be oppressors. A smartphone which currently costs $400, he predicted, might be as cheap as $20 in 12 years time.

“Technology will be a great leveller,” he said. “It empowers by its very nature. By ensuring universal access – to the cloud, to each other, to the world – we will create greater freedom and opportunity for all.

He added: “Sates will struggle to sell propaganda to the public as citizens get constant access to mobile phone and social networks. In times of war and suffering it will be harder to ignore the voices that cry out for help”.

But the Google executive also issued a series of warnings over where the future of the internet remains acutely vulnerable. As well as fretting about the increasing willingness of states to filter access to the web, Mr Schmidt admitted that it will take at least a decade to secure the web from criminal networks.

“Fixing this problem is a huge task,” he said.” Except for military networks, every single note on the web is connected and will need to be upgraded.”

He also expressed concerns about the difficulty citizens have in removing data about themselves from the web, remarking that the Internet currently had no “delete button.”

“A false accusation in your youth used to fade away; now it can remain forever,” he said. “I hope that ranking emerges that distinguishes between truth and falsehood to allow people to start over on a new footing.”

The Google executive has previously expressed reservations about the amount of personal information people leave on the internet – even once suggesting that younger generations might have to create new identities to escape their cyber record once they enter the work place.

His concerns over online privacy is perhaps surprising given that he has helped create a company that has made billions by perfecting the art of hoarding, storing and retrieving information on us.

Much of Mr Schmidt's speech was dedicated to whether we are dong enough to train future generations of engineers and software developers – a theme he has often expressed concern about. Last year he delivered a devastating critique of Britain's education.

In his latest speech he struck a more conciliatory tone saying he was “impressed with [the government's] willingness to engage on this crucial issue”. But he warned that more needed to be done to promote science and engineering to younger generations.