TikTok: Number 10 defends decision to ban social media app over security concerns after criticism from China
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It means users of Government-issued devices, bar officials given specific exemptions, will be prohibited from using the popular video-sharing application.
A spokesperson for the Chinese embassy in Britain accused ministers of acting "based on its political motive rather than facts".
But No 10 said a security review had concluded that Government data could be "potentially vulnerable" via the social media platform.
The Cabinet Office said the ban was being imposed because TikTok users are required to hand over data including contacts, user content and geolocation data.
TikTok has long said it does not share data with China but the country's intelligence legislation requires firms to help the Communist Party when requested.
Critics fear the policy could expose data to Beijing, with growing concerns about how Xi Jinping's administration could use technology against the West.
During Boris Johnson's premiership, ministers ruled that equipment produced by Chinese tech giant Huawei should be stripped out of the UK's 5G network following security advice and US sanctions on the firm.
The UK's TikTok decision followed action already taken by allies, with Prime Minister Rishi Sunak's administration having been under pressure from Conservative backbenches to follow Washington and the European Union's lead in outlawing it from devices used for official business.
A spokesman for the Prime Minister told reporters on Friday that a security review concluded that a devices ban "would be a prudent and proportionate step given the potential vulnerability of government data".
The analysis had found there were "risks around how sensitive information can be accessed and used" by the website, he added.
"Anyone who uses TikTok will know that it requires users to give permission for the app to access data stored on the device which is then collected by the company," the No 10 spokesman continued.
"So we think it's a prudent step to not allow it on Government devices."
While the ban applies to Government-issued devices, ministers and officials will still be able to use TikTok on their personal phones.
Energy Security Secretary Grant Shapps, an avid user of the platform, has made clear he will continue to view and post videos from his personal phone via the app while taking security precautions.
Along with personal phone use allowances, there will also be some "limited exemptions" on some Government devices made on a "case-by-case basis" where the video-sharing app is required for work purposes.
Downing Street said there was no plan to delete the No 10 account and has hinted that it could remain operational due to the need to communicate with the public on social media.
The Chinese embassy, in comments issued on Thursday, said the targeted ban would "undermine the confidence of the international community in the UK's business environment" while calling for London to "refrain from overstretching and abusing the concept of national security".
TikTok, owned by Chinese internet company ByteDance, said it was "disappointed" with the decision and said bans were based on "fundamental misconceptions and driven by wider geopolitics".
A spokesman for the firm said efforts were being made to make UK data even more secure and stressed that information shared by British users was not stored on China-based data centres.