The issue should demand the attention of “every citizen” and will not be “easily solved”, she said in a discussion organised by the Chatham House think tank in London.
Among the problems she identified were that, in the wake of the January attack on the capitol building in Washington DC, young people were now questioning whether democracy could produce results that are accepted not just by the majority but also by a vocal minority.
She described the events of 6 January as “beyond shocking, but sadly the attacks on democracy continue”.
These include attacks from people in the media and in public life, she said.
Ms Clinton also called for a “reckoning” for tech companies, who she accused of undermining the “ecosystem” she said was necessary for any democracy to function.
"What we have got in the tech world, on social media platforms is an algorithm driven conspiracy rabbit hole that people are enticed to go down and then are addicted to because it is like watching constant car crashes - you cannot turn away”, she told the audience on Zoom.
“If you cannot have an agreement on truth – how can a democracy make decisions,” she warned.
Ms Clinton’s race for the presidency coincided with allegations of Russian interference in American elections.
But Russia was not the only country in the world seeking to create divisions within other nations, she said.
Other countries such as Iran and China had been inspired by “how successful” Russia had been, she said.
She also told the event there was “also significant evidence of Russian involvement if not influence or interference in Brexit”.
She was responding to a question from former foreign secretary William Hague who said that one threat that had preoccupied since he left office was that of foreign interference in democracies.
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