Britain rejected calls from China and Russia for greater Internet controls on Tuesday at the opening of a major cyberspace conference but was criticized for suggesting curbs on social media after recent riots.

Ministers, tech executives and Internet activists are meeting over two days in London to discuss how to tackle security threats and crime on the Internet without stifling economic opportunities or freedom of speech.

While Western states worry about intellectual property theft and hacking, authoritarian governments are alarmed at the role the Internet and social media played in the protests that swept the Arab world this year.

Too many states around the world are seeking to go beyond legitimate interference or disagree with us about what constitutes 'legitimate' behavior, Foreign Secretary William Hague told the meeting.

We saw in Tunisia, Egypt and Libya that cutting off the Internet, blocking Facebook, jamming Al Jazeera, intimidating journalists and imprisoning bloggers does not create stability or make grievances go away ... The idea of freedom cannot be contained behind bars, no matter how strong the lock.

In September, China, Russia, Tajikistan and Uzbekistan proposed to the United Nations a global code of conduct including the principle that policy authority for Internet-related public issues is the sovereign right of states.

An anti-censorship group, however, accused Western governments of double standards, pointing out Prime Minister David Cameron briefly considered restricting online social networking media after riots swept English cities in August.

It's very easy to defend this case of black and white human rights against dictatorships around the world, but as soon as our own Western-style stability of the state is called into question then freedom of expression is expendable. There should be one rule for all, including western governments, John Kampfner, chief executive of Index on Censorship, told the conference.

Cyber security experts say western states are hoping to regain the initiative in the debate with this conference.

NO IMMEDIATE AGREEMENT LIKELY

The agenda is so broad and the topic is so vast, so don't expect it to be sorted out at this conference, Swedish Foreign Minister Carl Bildt told reporters, adding that he believed over time some form of international agreement would come.

We are all going to be so dependent on the networks of the world that we will have increasing recognition over the years to come that we need some global standards.

Around 60 countries, including China, Russia and India, are represented at the conference as well as tech industry figures such as Jimmy Wales, founder of Wikipedia, and senior executives from Facebook and Google.

Wales told the conference he believed many current attempts to regulate the flow of information -- such as British court superinjunctions which celebrities have used to block discussion of certain embarrassing stories -- were bad law.

We see all the time these kinds of laws, he said. Maybe there are better ways than to rely on government control.

U.S. Secretary of State Hillary Clinton canceled due to her mother's illness. Her planned afternoon speech would be given by teleconference by Vice President Joe Biden, officials said.

One area where there are better prospects of international agreement is cooperation to tackle conventional crime and child pornography.

A closed session will deal with the aspect of the Internet's rise that has seized most attention -- threats to international security including hacking and potential cyber warfare.

On the eve of the conference, the head of Britain's communications spy agency said UK government and industry computer systems faced a disturbing number of cyber attacks, including a serious assault on the Foreign Office's network.

(Additional reporting by Georgina Prodhan, Peter Apps, Michael Holden; Editing by Robert Woodward)

London