Eight major US web companies including Apple, Google and Facebook made a joint call on Monday for tighter controls on how governments collect personal data, intensifying the furore over online surveillance.

In an open letter to US President Barack Obama and Congress, the companies said recent revelations showed the balance had tipped too far in favor of the state in many countries and away from the individual.

In June, former National Security Agency contractor Edward Snowden exposed a top secret government surveillance program that taps into communications on cables linking technology companies' various data centers overseas.

After Snowden's disclosure, many of the big Internet companies warned that US businesses may lose revenue abroad as distrustful customers switched to local alternatives.

"We understand that governments have a duty to protect their citizens," said the letter from the eight giant technology companies which also included Microsoft Corp, Twitter, LinkedIn Corp, Yahoo Inc and AOL Inc.

"But this summer's revelations highlighted the urgent need to reform government surveillance practices worldwide."

The companies have detailed their "Reform Government Surveillance" campaign on a website, calling on the US government to take the lead by limiting how much user information a government can collect.

"People won't use technology they don't trust," Microsoft General Counsel Brad Smith said on the website. "Governments have put this trust at risk, and governments need to help restore it."

The campaign also calls on governments to limit surveillance to specific, such as known users and not to collect data in bulk, and asks that companies have the right to publish the number and nature of government demands for user information.

Reuters