More than 110 child-health advocates have called on Facebook chief executive Mark Zuckerberg to pull the firm’s Messenger Kids app aimed at under 13s, warning of the dangers of social media for children.

In an open letter led by the Boston-based Campaign for Commercial-Free Childhood, signed by doctors, educators and child health experts including baroness Susan Greenfield, warn that “younger children are simply not ready to have social media accounts”.

The authors write: “At a time when there is mounting concern about how social media use affects adolescents’ wellbeing, it is particularly irresponsible to encourage children as young as pre-schoolers to start using a Facebook product.”

The standalone Messenger Kids app was launched in December targeting children under 13 with strict parent controls that include contact approvals, screened content and safety filters to prevent children sharing inappropriate material. It contains no ads and Facebook says data collected from it will not be used for advertising purposes.

But the launch of the app was attacked by commentators and British health secretary Jeremy Hunt, who said the firm should “stay away from my kids”.

The open letter authors said Messenger Kids was likely to increase the amount of time pre-school and elementary age children spend with their devices.

“In a landscape of ubiquitous technology that undermines children’s emotional growth, the last thing the youngest among them need is a powerful enticement to move their friendships online” said Dr Sherry Turkle, Abby Rockefeller Mauzé professor of the social studies of science and technology at MIT, and author of the book Reclaiming Conversation.

“It’s galling to see Facebook target young children at a time when evidence is mounting that excessive social media use negatively impacts kids and teens’ wellbeing,” said Josh Golin, executive director of the Campaign for Commercial-Free Childhood.

Facebook said it developed Messenger Kids with the help of online safety experts including the National PTA and Blue Star Families. It is designed to connect children to relatives and friends through text, photos and video chat while making parents the gatekeepers. It is fully compliant with the US Children’s Online Privacy and Protection Act, the social network said.

“As children spend more and more time on digital devices, they lose the healthy capacities to cultivate moments of quiet and solitude that are so crucial for developing empathy and healthy relationships,” said Turkle.

Jenny Radesky, MD, a developmental behaviour paediatrician and media researcher at the University of Michigan, said those under 13 years old find it hard to grasp concepts such as privacy and personal data. “They’re just starting to build awareness about their identity, their role in relationships, and morality,” she said. “Combine that immaturity with the problematic interactions that often happen on social media, and it could be really messy.”

US federal law prohibits companies from collecting personal information on those under 13 without parental consent. However, millions of children are already on Facebook, with or without their parents’ permission, said Stephen Balkam, chief executive of the nonprofit Family Online Safety Institute, who saw the launch of Messenger Kids as a pragmatic approach to the situation.

The open letter joins a chorus of discontent directed towards the impact of social media, and in particular Facebook, on society and the young.

Industry insiders including former Facebook president Sean Parker, SalesForce CEO Marc Benioff and Apple chief executive Tim Cook have all recently expressed concerns over the use of social media by children.

“Parents, health professionals, and even investors are standing up to tell tech giants that they’ve gone too far,” said Golin. “This is a pivotal moment, and Silicon Valley executives must decide if they care about the welfare of children, families and society, or only about hooking users and pursuing profits.”

A Facebook spokesperson said: “We worked to create Messenger Kids with an advisory committee of parenting and developmental experts, as well as with families themselves and in partnership with the PTA. We continue to be focused on making Messenger Kids be the best experience it can be for families. We have been very clear that there is no advertising in Messenger Kids.”