Donald Trump’s online supporters have flocked to Telegram, an encrypted messaging app that has been beset by allegations of harbouring criminals and terrorists, after the social networking site Parler was forced offline.

Telegram became the second-most downloaded app in America on Sunday as users looked for a new home online after Mr Trump was suspended from Facebook and Twitter, and as tech companies cut off Parler, a free speech social network that had sprung up as an alternative.

More than half a million people in the US have downloaded the app since last Wednesday, and posts on Parler had urged users to move to Telegram before Parler was taken offline on Monday.

High-profile allies and backers of the President, including his son Donald Trump Jr and former attorney Sidney Powell, post frequently on the Telegram app. Meanwhile, groups for former Parler users or those devoted to the President amassed tens of thousands of users.

Messages sent over Telegram are encrypted and the app has historically been used to resist censorship or surveillance in countries such as Russia and Iran.

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On Saturday, after Apple and Google had removed the Parler app from their smartphone download stores, Telegram founder Pavel Durov said the companies “pose a much bigger problem for freedoms than Twitter”. Posting on the app, he said Telegram was working on a way to continue to work on iPhones even if Apple removes the app from the App Store.

Telegram was installed around 545,000 times in the US between Wednesday and Sunday, almost three times as much as the same period a week earlier, according to data company Sensor Tower. Download numbers were also boosted by a controversy over a new privacy policy for rival app WhatsApp.

Telegram functions in a similar way to apps such as WhatsApp, allowing one-to-one and group chats, but also lets public figures set up “channels” to broadcast to followers. Up to 200,000 people can join public group chats.

Jen Goldbeck, a professor of information studies at the University of Maryland, said Telegram could become a longer-term home for devoted Trump supporters than Parler because it is less likely to be taken offline. “If it was just used by these alt-right groups, that may give Apple or Google some control, but these are general messaging apps that people use for legitimate reasons.”

She said because the app was reliable and easy to use, it could be more attractive than sites like Gab, 4chan and TheDonald.win, which supporters have used. "Those are weird platforms for just the average MAGA supporter they don’t feel like regular social media and they can be a little difficult to penetrate and understand. If you’re not a committed supporter you want to find a place that feels easy to use and stable and not risky."

Mr Durov did not respond to an email seeking comment.

Separately on Monday, Parler sued Amazon, whose decision to ban the service from its web hosting service led to it going offline. It is seeking to have Amazon reinstate the company’s service.