TikTok is being banned from Government phones and other devices with immediate effect following security fears.
Cabinet Office Minister Oliver Dowden told MPs that a high-level review had found there could "be a risk around how sensitive Government data is accessed and used by certain platforms".
Mr Dowden said TikTok would be outlawed with immediate effect on Government devices - and ministers and officials would only be able to access apps on a pre-approved list on their official phones.
But ministers will still be able to use TikTok on their personal phones, with Cabinet Minister Grant Shapps insisting he will continue to post from his own phone.
In a bizarre move, the Energy Security Secretary posted a clip from the Wolf Of Wall Street in which Leonardo DiCaprio, portraying a New York stockbroker, declares he is "not f****** leave" and the "show goes on".
Mr Shapps, who has 14,400 followers, wrote on TikTok: "This morning the Government announced a TikTok ban on Government devices. That's sensible.
"I've never used TikTok on Government devices and can hereby confirm I will NOT be leaving TikTok anytime soon! #politics #news #foryoupage #FYP #trend #wolfofwallstreet #imnotleaving #tiktok."
Labour's Angela Rayner accused the Government of "closing the stable door after the horse has bolted" and said they were always "behind the curve with sticking plaster solutions".
The European Commission and the US Congress have already outlawed the app, owned by Chinese internet company ByteDance, following concerns about possible cyber attacks.
Rishi Sunak has been under pressure from his own MPs to crack down on use of TikTok, prompting Security minister Tom Tugendhat to National Cyber Security Centre chiefs to launch a probe.
Announcing the move, Mr Dowden said: “The security of sensitive government information must come first, so today we are banning this app on government devices. The use of other data-extracting apps will be kept under review.
“Restricting the use of TikTok on Government devices is a prudent and proportionate step following advice from our cyber security experts.”
But Ms Rayner said the Government has been forced into another U-turn.
"Two weeks, two ministers, two completely different policies later, and it is the same pattern over and over again, a Government behind the curve with sticking plaster solutions forced to lurch into a U-turn at the last minute," she said.
Science and Technology Secretary Michelle Donelan had said on Wednesday that the public can continue to use the app as the UK has "the strongest data protection laws in the world".
Former Tory leader Sir Iain Duncan Smith said ministers and senior civil servants should be told to remove TikTok from their personal phones as well.
"Private phones are used for communications and I honestly don't believe that whatever the complaints are, that the reality is that these private phones will never be used for Government business," he said.
Ex-Culture Secretary Nadine Dorries, a frequent poster on TikTok when she was in Government, tweeted: "My phone is personal. Today I removed Tik Tok and I think all MPs should do likewise."
But Energy Security Secretary Grant Shapps said he will continue to use it on his personal phone while taking security precautions.
Downing Street said there were no plans to delete the No10 TikTok account.
Asked what this means for parents who will worry over their children’s use of TikTok, the PM’s spokesman said: “This is about a potential vulnerability of government data so parents should absolutely be reassured on that point.
"Of course, there is already guidance on social media and the broader risks to young children and the Online Safety Bill seeks to address some of that for example."
The move is likely anger Beijing, which has accused the US of spreading disinformation and suppressing TikTok amid reports the White House is calling for its Chinese owners to sell their stakes.
But critics fear the policy could expose western data to Beijing.
TikTok has long said it does not share data with China but Chinese intelligence legislation requires firms to help the Communist Party when requested.
Parliament's TikTok account was shut down last year after MPs raised concerns about the firm's links to China.
A TikTok spokesperson said: "We are disappointed with this decision. We believe these bans have been based on fundamental misconceptions and driven by wider geopolitics, in which TikTok, and our millions of users in the UK, play no part.
"We remain committed to working with the government to address any concerns but should be judged on facts and treated equally to our competitors.
"We have begun implementing a comprehensive plan to further protect our European user data, which includes storing UK user data in our European data centres and tightening data access controls, including third-party independent oversight of our approach."
