Chuck Schumer, the most senior Democrat in the Senate, has urged the government to investigate TikTok, describing the China-owned social media app as “a potential counter-intelligence threat we cannot ignore” and warning it could be used to interfere in US elections.

TikTok, which allows users to share short videos online, has enjoyed wild success since it launched in 2017, and has been downloaded more than 1bn times.

Schumer and Tom Cotton, the Republican senator from Arkansas, co-wrote a letter to the acting director of national intelligence on Wednesday. The pair said they were writing “to express our concerns about TikTok … and the national security risks posed by its growing use in the United States”.

They wrote: “TikTok reportedly censors materials deemed politically sensitive to the Chinese Communist party, including content related to the recent Hong Kong protests, as well as references to Tiananmen Square, Tibetan and Taiwanese independence, and the treatment of the Uighurs.

“The platform is also a potential target of foreign influence campaigns like those carried out during the 2016 election on US-based social media platforms.”

But in September the Guardian revealed how ByteDance, the Beijing-headquartered technology company that owns TikTok, is using the app to further Chinese foreign policy aims abroad. Leaked documents showed how TikTok had instructed its moderators to censor videos that mention Tiananmen Square or Tibetan independence, or which may be critical of China.

“With over 110m downloads in the US alone, TikTok is a potential counter-intelligence threat we cannot ignore,” Schumer and Cotton wrote.

“Given these concerns, we ask that the intelligence community conduct an assessment of the national security risks posed by TikTok and other China-based content platforms operating in the US and brief Congress on these findings.”