Two U.S. senators are less than impressed with Meta's reported plans to open up its Horizon Worlds metaverse platform to users as young as 13 — so, they're urging Mark Zuckerberg to reconsider.

Over the weekend, Senators Ed Markey (D-Mass.) and Richard Blumenthal (D-Conn.) published excerpts from a letter they sent to Zuckerberg. In those excerpts, they accused Meta of trying to "target young people" specifically to "maximize profit," noting the company's struggles to attract users to its flagship metaverse product, Horizon Worlds.

"With a documented track record of failure to protect children and teens, Meta has lost parents', pediatricians', policymakers', and the public's trust," Markey and Blumenthal wrote, adding: "Your plans to imminently pull these young people into an under-researched, potentially dangerous virtual realm with consequences for their physical and mental health is unacceptable."

The politicians were responding to a recently leaked internal Meta memo, reported on by The Wall Street Journal in February, which outlined plans to open access to Horizon Worlds to users between the ages of 13 and 17 as early as this month.

Horizon Worlds is an app where users can build and explore virtual worlds while playing games and interacting with other users. It's accessible with an Oculus Quest virtual reality headset, and only accessible to users over the age of 18 — but the internal memo reportedly noted that Horizon Worlds could only succeed with the support of younger users.

Meta declined to comment on the senators' letter, pointing instead to a statement to the Journal last month, which said bringing younger users onto Horizon Worlds would come with "age-appropriate tools and protections."

Experts agree: The metaverse could be highly damaging for teens

Last year, CNBC Make It discussed this exact issue with psychologists and online safety experts, who said metaverse apps like Horizon Worlds won't just present the same bullying and harassment problems for children and teens as existing social media platforms.

Such apps could make the problem even worse, they noted.

"This is just an exacerbation of the problems that we've already started to see with the effects of social media," said Mitch Prinstein, a clinical psychologist and chief science officer for the American Psychological Association. "This is creating more loneliness. This is creating far more body image concerns [and] exposure to dangerous content that's related to suicidality."

In 2021, the Journal reported that Meta had conducted internal studies showing how its Instagram app could be toxic and harmful for younger users. Meta later canceled its plan to roll out a version of Instagram for kids, and introduced new features meant to increase teens' safety on its apps.

The newly reported Horizon Worlds plan raises those same issues again, and is "particularly concerning in light of your consistent failures to protect young users," Markey and Blumenthal wrote.

Adding younger teenagers to an immersive online platform could allow them to potentially interact with strangers — and since launching Horizon Worlds in 2021, Meta has been forced to deal with reports that some users' digital avatars were being harassed or even groped.

Last year, the company released a "personal boundary" feature aimed at preventing further harassment. The feature appears to do little to address the specific issue of child grooming.

Meanwhile, younger users are reportedly already finding their way onto Horizon Worlds by using their parents' virtual reality headsets or creating fake Facebook accounts, leading to further concerns about user safety.

In their letter to Zuckerberg, Markey and Blumenthal emphasized those concerns, writing: "We call on you to immediately halt Meta's plan to bring teen users onto Horizon Worlds."

DON'T MISS: Want to be smarter and more successful with your money, work & life? Sign up for our new newsletter!

Get CNBC's free Warren Buffett Guide to Investing, which distills the billionaire's No. 1 best piece of advice for regular investors, do's and don'ts, and three key investing principles into a clear and simple guidebook.