Hillary Clinton says Facebook has "a long way to go" when it comes to disclosing the extent to which Russians used the platform to interfere with the 2016 election.
Appearing Thursday on The Rachel Maddow Show, Ms Clinton said Facebook has "just begun to own up. They have a long way to go before they get where they need to be."
She also suggested that other tech companies had a duty to disclose whether their platforms were used for Russian interests.
Facebook acknowledged earlier this month that Russian-linked firms purchased ads during the 2016 campaign on certain divisive issues, although it has not found that spots were purchased to advocate for or against a specific candidate.
That has put a new level of scrutiny on Facebook, and whether it was used by Russian interests to sow discord in 2016 by spreading fake news stories and establishing fake accounts. Ms Clinton cited those examples as ways that the regime of Vladimir Putin attempted to interfere with the electoral process.
"We continue to investigate and will continue to work with the relevant investigative authorities," a Facebook spokesman said.
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Ms Clinton said "transparency" was the best counter to Putin.
Ms Clinton said Mr Putin's efforts to interfere with the election was "personal", given the past criticisms she had made about his regime while she was Secretary of State.
"He saw me as someone who would stand up to him," she said, adding that she thinks Mr Putin has a broader goal of trying to "destabilise democracy" among western nations.
Ms Clinton chided US President Donald Trump's administration for launching an investigation into voter fraud - which she called "voter suppression" - rather than of Russian interference in the 2016 campaign. "That is not happening," she said.
Ms Clinton said if she were elected, she would have established an independent commission with subpoena power.
"We're going to get to the bottom of this so it never happens again."