New rules governing social media companies in India will make it hard for the firms to operate and give authorities the power to censor internet users, campaigners warned after WhatsApp filed a suit against the Indian government.

WhatsApp, a unit of Facebook, filed a legal complaint in Delhi against the Indian government, seeking to block regulations taking effect on Wednesday that experts say would compel the firm to break privacy protections. The lawsuit asks the Delhi High Court to declare one of the rules a violation of privacy rights in India's constitution since it requires social media firms to identify the "first originator of information" when authorities demand it.

"This is probably the most significant privacy case in India," said Nikhil Pahwa, founder of technology publication Medianama. "Yes, platforms need to be regulated. But in a manner that gives users power over platforms. Not in a manner that empowers government and allows them to use platforms to control user speech," he said in a tweet.

WhatsApp, which has nearly 400 million users in India, said it will "continue to engage with the government of India on practical solutions aimed at keeping people safe, including responding to valid legal requests for the information available to us".

"Requiring messaging apps to 'trace' chats is the equivalent of asking us to keep a fingerprint of every single message sent on WhatsApp, which would break end-to-end encryption and fundamentally undermines people's right to privacy," WhatsApp said in a statement cited by NDTV news.

The lawsuit comes amid clashes between Prime Minister Narendra Modi's government and tech giants including Facebook, Google parent Alphabet, and Twitter, in one of their key markets. The government has demanded that the firms remove what it has said is misinformation on the COVID-19 pandemic ravaging India, as well as criticism of the government's response to the crisis and farmers' protests earlier.

The new Intermediary Guidelines and Digital Media Ethics Code, which was unveiled in February, requires that big social media firms appoint Indian citizens to key compliance roles, remove content within 36 hours of a legal order, and set up a mechanism to respond to complaints. The firms stand to lose protection from lawsuits and criminal prosecution if they fail to comply.

"This means they will find it very difficult to operate in India as they will be liable in all types of legal cases which will include claims of monetary fines or even criminal prosecutions," said Apar Gupta, executive director of Internet Freedom Foundation, a digital rights groups in Delhi. "This will have a chilling impact on internet users in India as platforms will censor more speech under the threat of enforcement," he told the Thomson Reuters Foundation.

Across Asia, several countries have introduced a slew of internet and data-use legislation in recent months, with human rights groups warning that these measures raise the risk of mass surveillance and violations of free speech. At least six other petitions have been filed in Indian courts challenging the new social media code, according to the Internet Freedom Foundation.

The code has raised "major concerns around freedom of speech and expression and will be detrimental to the principle of a free and open internet", said Prasanth Sugathan, legal director of digital rights group, which has filed a petition. "More social media intermediaries may approach the courts," he added.