Technology's biggest companies have started a public campaign to limit government surveillance of users, Mashable reported.

The coalition, which is led by Microsoft and Google and includes Apple, Facebook, Twitter, AOL, Linkedin and Yahoo, published an open letter in the form of full-page ads, in national newspapers and opened a website at reformgovernmentsurveillance.com.

In the letter, the companies present a plan to regulate online spying and called for the U.S. president and Congress to lead a worldwide effort to restrict it. They said online surveillance undermines the freedoms of people.

"We understand that governments have a duty to protect their citizens. But this summer's revelations highlighted the urgent need to reform government surveillance practices worldwide," the letter said. "The balance in many countries has tipped too far in favor of the state and away from the rights of the individual - rights that are enshrined in our Constitution. This undermines the freedoms we all cherish."

The group requested the government's authority be imposed with "sensible limitations on their ability to compel service providers to disclose user data," and that they should limit surveillance to specific, known users for lawful purposes, and should not undertake bulk data collection of Internet communications. They're also demanding an increased oversight and accountability, transparency about government demands, respect the ability of data to flow or be accessed across borders and to avoid conflicts among governments.

The initiative comes after "a string of leaks this summer" detailed the National Security Agency's extensive surveillance of people in the U.S., including spying on data centers of the companies involved in the coalition and other tech companies.

According to Engadget, the companies' efforts began in October when they petitioned Congress to reform the U.S. government's surveillance policies.