Former US President Barack Obama has warned against the irresponsible use of social media, in a rare interview since stepping down in January.
He warned that such actions were distorting people's understanding of complex issues, and spreading misinformation.
His successor Donald Trump is a prolific user of Twitter, but Mr Obama did not mention him by name.
Mr Obama was quizzed by Prince Harry on BBC Radio 4's Today programme.
Prince Harry, fifth in line to the throne, is one of several prominent figures who are guest-editing the programme over the Christmas period.
The ex-president said those in positions of power should be careful when posting messages, warning that social media is distorting civil discourse.
He expressed concern about a future where facts are discarded and people only read and listen to things that reinforce their own views.
Mr Trump has been accused of overusing Twitter, though he maintains it allows him to connect directly with the American people.
On handing power to Mr Trump, Mr Obama described mixed feelings, given "all the work that was still undone".
"Concerns about how the country moves forward but, you know, overall there was serenity there," he adds.