A potential ban in China on software to avoid the country's censors could make it "impossible" to communicate privately online, the German ambassador warned Monday.
German envoy Michael Clauss said the possible prohibition of virtual private networks (VPNs) and the recent blockage of WhatsApp have raised concerns among foreign businesses.
China has one of the world's most restrictive mechanisms for online censorship, deleting content deemed politically sensitive while blocking certain Western websites and apps such as Facebook, Twitter and Google.
Some businesses and individuals employ VPNs to bypass the so-called "Great Firewall" and access the unfettered web.
But Beijing mandated in January that all developers must obtain government licences to offer such software, and there has been mounting concern that it might ban them outright.
"It would be difficult if not practically impossible for individuals and companies alike to communicate in a safe and confidential electronic environment" if such a policy were enforced, Clauss said in a statement posted to the embassy website.
"If digital communication was throttled, it could have detrimental effects for China's relationship with the outside world, including Germany," Clauss said.
Clauss said the Communist Party's national congress, which opens Wednesday, will give signals "on whether the trend of further opening up is meant to continue or not."
The intermittent blocking of Facebook's messaging app WhatsApp ahead of the party congress had also caused "growing concern" over China's intention to further restrict access to international information, Clauss added.
Many Chinese activists favour WhatsApp over local messaging apps because of its end-to-end encryption function -- one likely viewed unfavourably by authorities.
As well as the WhatsApp block, China enacted a new cybersecurity law this year, tightening restrictions on online freedom of speech and imposing new rules on service providers, including one requiring tech companies to store user data inside the country.
Many in the foreign business community are complaining of the law's "extensive scope" and "unpredictable implementation," Clauss said.
"In the 'offline' world, our overlapping economic and political interests bring us closer together, but this trend may not be sustainable if excessive cyber controls drive us apart," Clauss said.
A 2016 report by US think tank Freedom House found that China had the most restrictive internet policies of 65 countries it studied, ranking below Iran and Syria.