The US, China and Russia have refused to endorse a French-backed agreement designed to regulate the Internet and bolster cyber security, despite the approval of 51 other countries including all members of the European Union.

The Paris Call for Trust and Security in Cyberspace was launched by French President Emmanuel Macron on Monday and represents an attempt to set clear rules for the use of cyber-weapons.

At an event organised by UNESCO, the French leader set out his ambitions for stronger international regulation of the Internet and better cooperation on cyber-attacks, foreign meddling in elections, online censorship and hate speech.

But the refusal of Washington DC, Moscow and Beijing to sign up to the agreement represents a serious blow for the initiative.

“The internet is a space currently managed by a technical community of private players. But it’s not governed. So now that half of humanity is online, we need to find new ways to organize the internet,” a French official said. “Otherwise, the internet as we know it today — free, open and secure — will be damaged by the new threats.”

President Macron said he planned to continue to pressure the US and others to sign the pledge. While the Trump administration is not currently supporting the initiative, US technology companies, such as Google, Facebook and Microsoft, are backing it.