Telegram, which offers encrypted chat services, today said 25m new users had signed up in the last 72 hours alone.
This is compared to the 1.5m daily additions it averaged last year, while the app’s total user base has now passed 500m.
While the new policy does not apply in the UK or Europe, it has sparked criticism from users and privacy groups around the world.
“People no longer want to exchange their privacy for free services,” wrote Telegram founder Pavel Durov. “They no longer want to be held hostage by tech monopolies that seem to think they can get away with anything as long as their apps have a critical mass of users.”
“With half a billion active users and accelerating growth, Telegram has become the largest refuge for those seeking a communication platform committed to privacy and security.”
Rival messaging service Signal has also enjoyed a rise in new users in the wake of Whatsapp’s privacy shake-up.
The platform suffered from delays in sending out verification codes last week after it was inundated with new registrations.
“We continue to shatter traffic records and add capacity as more and more people come to terms with how much they dislike Facebook’s new terms,” it wrote in a tweet.
Both Telegram and Signal, which offer encrypted services, position themselves as more secure alternatives to the major social media apps.
They have also benefited from an exodus of Donald Trump supporters from Silicon Valley tech giants after the president was blocked for inciting violent riots at the Capitol last week.
Trump’s ban from Twitter and Facebook had sparked speculation that he would move to self-styled free speech app Parler, which is popular with far-right extremists.
However, Parler has been taken offline after Amazon pulled its support and both Apple and Google removed it from their app stores.
Despite the growth of rival platforms, Whatsapp remains by far the largest messaging app with over 2bn users.