Perverts are using it to watch youngsters’ broadcasts and bombard them with requests to remove their clothes or make explicit videos.
The grooming was revealed by the BBC, which then handed the evidence to police.
Periscope, which has more than 10 million users, allows people to film themselves on their smartphones and broadcast this live to anyone in the world.
In recent years it has been criticised for its users’ ability to globally broadcast live sport which would normally require viewers to pay subscription fees.
The BBC investigation found people sending messages to children as young as nine that included requests for them to “show skirt under desk” or “take off your top”.
Others sent pervy messages such as “ever had sex?”, “what’s your cup size sexy?” and “can I send you money for a show?”
Claire Lilley, head of online child safety at the NSPCC, called the investigation’s findings “disturbing”.
To see someone “so clearly groomed for sexual purposes by a pack of people online” was “shocking”, she added.
A spokesperson for Pericope’s owner, Twitter, stated: “We have a strong content moderation policy and encourage viewers to report comments they feel are abusive.
“We have zero tolerance for any form of child sexual exploitation.”
Earlier this year a teenage girl was jailed for live-streaming a video of her friend being raped via the Periscope app.
Marina Lonina, 19, was sentenced in Columbus, Ohio, on Monday after pleading guilty to obstructing justice under a deal with prosecutors.
Story by The Sun