The National Association of Attorneys General (NAAG) is urging Facebook to cancel its plans to develop an Instagram platform exclusively for children under the age of 13.

A group of 44 state and territory attorneys general signed a letter addressed to Facebook Chief Executive Mark Zuckerberg, urging him to abandon plans to launch the platform for school-age users.

"Use of social media can be detrimental to the health and well-being of children, who are not equipped to navigate the challenges of having a social media account," the letter reads.

The letter goes on. "Further, Facebook has historically failed to protect the welfare of children on its platforms. The attorneys general have an interest in protecting our youngest citizens, and Facebook's plans to create a platform where kids under the age of 13 are encouraged to share content online is contrary to that interest."

In March, Facebook announced its intent to build a platform for children in an internal company post.

"I'm excited to announce that going forward, we have identified youth work as a priority for Instagram and have added it to our H1 priority list," Vishal Shah, Instagram's vice president of product, wrote on an employee message board, first reported by BuzzFeed.

"We will be building a new youth pillar within the Community Product Group to focus on two things: (a) accelerating our integrity and privacy work to ensure the safest possible experience for teens and (b) building a version of Instagram that allows people under the age of 13 to safely use Instagram for the first time."

A spokesperson for Facebook confirmed the news to The Guardian. Facebook is building a "parent-controlled" version of Instagram for young kids, similar to the Messenger Kids app that is available for kids between the ages of six and 12.

"Increasingly kids are asking their parents if they can join apps that help them keep up with their friends. Right now, there aren't many options for parents, so we're working on building additional products … that are suitable for kids, managed by parents," the spokesperson told The Guardian.

"We're exploring bringing a parent-controlled experience to Instagram to help kids keep up with their friends, discover new hobbies and interests, and more."

In their letter, the attorneys general expressed concerns over Facebook's plan for the app and how it might impact children. They cited research that social media can be harmful to the physical, emotional and mental wellbeing of children, as well as concerns about cyberbullying, privacy and sexual abuse issues.

"It appears that Facebook is not responding to a need, but instead creating one, as this platform appeals primarily to children who otherwise do not or would not have an Instagram account," the bipartisan group wrote.

Facebook says that the app will actually allow parents to have more access to their children's online presence.

"As every parent knows, kids are already online. We want to improve this situation by delivering experiences that give parents visibility and control over what their kids are doing," a Facebook spokesperson said in a statement to CNN Business.

"We are developing these experiences in consultation with experts in child development, child safety and mental health, and privacy advocates. We also look forward to working with legislators and regulators, including the nation's attorneys general. In addition, we commit today to not showing ads in any Instagram experience we develop for people under the age of 13."

Instagram doesn't allow users under the age of 13 to create an account. Because there's no real age verification however, children can create accounts by simply lying about their birth year.

Even on a platform designed for kids, the attorneys general argue that children "may not fully appreciate what content is appropriate for them to share with others, the permanency of content they post on an online platform, and who has access to what they share online. They are also simply too young to navigate the complexities of what they encounter online."