The warning to representatives of 55 governments and some 700 companies of the Asia-Pacific region, was made by Marc Rotenberg, the 39-year-old executive director of the Washington-based Electronic Privacy Information Center (EPIC), who Business Week calls "The Web's top privacy activist."

Tedson Meyers, former legal counsel to the PTC, told delegates at the conference, that Rotenberg "who says he never accepts speaking fees" had been invited to deliver the keynote address on Wednesday because as leaders in modern technology the delegates had a duty to help maintain freedoms in times of crisis.

"Freedom is the quintessential American concept, and it must be balanced with security," Meyers said.

Since the terrorist destruction of the World Trade Center towers in New York, Rotenberg said, citizens still had a right to privacy in their communications even though the authorities had stepped up surveillance of the world’s networks. In the commercial world, companies had an obligation to protect the privacy of credit card details or other personal data on individuals.

"In the post-September 11 world, we have to find a balance on the right to secrecy and privacy and the government’s concerns about security. There is a law protecting the privacy of telephone calls and efforts have to be undertaken to safeguard our basic freedoms even in times of national crisis," Rotenberg said.

Rotenberg, a graduate of Harvard University and Stanford Law School, is a member of the bar of the United States Supreme Court. He teaches information privacy law at Georgetown University Law Center and is a contributing editor to the Government Information Quarterly. He is also the secretary of the international human rights organization, Privacy International.

"In every discussion we have on the advantages of new technology, this question of balancing security and our rights is raised nowadays. Shortly after the attacks in the United States, our Congress embarked on new security legislation. Even as privacy rights of our citizens are being diminished, the government's security duty is being stepped up," he said.

Rotenberg said he did not like two new systems, known as Carnivore and Magic Lantern, currently used by the US security agencies to monitor people using the Internet. The Carnivore system enables the government to go through traffic on the internet by looking for keywords, and then logging onto the message. The more sophisticated Magic Lantern system enables it to log onto an individual's computer through a secret program that is even capable of monitoring that person's key strokes.

He also said he did not like the way companies are able to retain credit card details or the personal telephone numbers, e-mail or home addresses of individuals, which could then either be sold for profit by the company in question, or passed on to the police without the person's knowledge.

He told his audience, which included some of the world's leading computer and communications technology experts, that last year he had, through the courts, successfully stopped plans of the Internet marketing company, Double-Click Inc. to merge data on the on-line behavior of Internet users "including their addresses and purchasing habits" and then sell it without notifying the users. "There is this self-interested industry view that urges people to relinquish their privacy for all sorts of benefits. But my view is that if you lose your right to privacy, you lose your right to freedom," Rotenberg said.

Rotenberg, who himself lost a close family member aboard one of the aircraft which flew into the World Trade Center, has also targeted the Clinton Administration and Intel since he founded EPIC in 1994. Its funding comes from diverse non-profit groups including the Ford Foundation and the conservative Fund for Constitutional Government. The group’s threat of boycott last year helped stop Intel from activating technology in its Pentium III chips which would have made it easier to monitor the Internet usage of individuals, he said.

Citing what he called the “new architecture of surveillance”, Rotenberg said he was keeping a close eye on moves by state and federal authorities to develop new identity cards, or adapt driving licenses that could easily be checked nationwide. The smart cards would be encoded with digitized fingerprints, face scans and other "biometric" data, as well as bank details. He was also equally concerned about the use of "facecams" in public places where cameras linked to a national data base with millions of faces would be capable of identifying an individual within seconds.

"Once this sort of technology is gets into place, it is going to be difficult to prevent it developing further," he said, adding that he was sensitive to the needs of national security in the fight against terrorism, and of forgery and other crime. "What is done by means of technology in times of national crisis is difficult to undo once the crisis subsides."

These developments meant that ordinary citizens had every right to use modern encryption programs to protect their privacy.