A bill aimed at choking off US exports of technology used for Internet surveillance or censorship was introduced in the House of Representatives on Thursday.

"It's unconscionable that US technology is putting democracy activists at risk," said Representative Chris Smith, a Republican from New Jersey who is behind the Global Online Freedom Act.

"US companies should not, knowingly or unwittingly, be providing the technology used by repressive regimes to hunt down and punish human rights activists.

"This bill will stop the vicious merry-go-round we are now on of exporting Internet-restricting technologies from the US that we then have to spend millions of dollars helping activists circumvent," Smith said.

The legislation would prohibit American companies from exporting hardware or software that could be used for online surveillance or censorship to nations that restrict the Internet.

It would also require Internet companies listed on US stock exchanges to disclose to American regulators their practices in collecting and sharing personally identifiable information and steps taken to notify users when removing content.

"This will apply not only to US companies but to the increasing number of foreign IT companies that raise capital here on our stock exchanges, including a large number of Chinese Internet companies that will soon have to report their practices to the (Securities and Exchange Commission)," Smith said.

At a hearing of the House Subcommittee on Africa, Global Health and Human Rights, Smith said the Internet has been transformed over the past few years "from a freedom plaza to dictator's best friend."

"Every day we learn of more democratic activists being arrested through the use of a growing array of Internet censorship and surveillance tools, abused by the governments of China, Belarus, Egypt, Syria and many other countries," he said.

Clothilde Le Coz, Washington director of Paris-based Reporters Without Borders, told the hearing the legislation was a welcome step towards making companies more responsible and should be matched by similar efforts in Europe.

"There is a criminal cooperation between Western hi-tech companies and authoritarian regimes," Le Coz said.

"The surveillance tools sold by these companies are used all over the world by armed forces, intelligence agencies, democratic governments and repressive regimes.

"The leading exporters of these technologies include the United States, France, Germany, Italy, United Kingdom and Israel," she said. "Companies should have a responsibility when selling their technologies abroad."

Another witness, Elisa Massimino, president and chief executive of Human Rights First, said many companies "really have not gotten their heads around what it means to be responsible for the end use of their products."

"Companies have to feel that they're being watched," Massimino said.