Facebook and Instagram have become a "breeding ground" for child predators, the New Mexico attorney general has claimed in a lawsuit.

Raul Torrez said his office had set up fake accounts that were sent phallic pictures and "solicitations".

He asked the court to order the firm to make changes to protect its youngest users, alleging it has "refused" to do so voluntarily.

In response, Meta said it worked hard to root out predators.

But New Mexico said searches by its investigators revealed that some kinds of exploitative child material was "ten times" more prevalent on Facebook and Instagram than on sites such as Pornhub and OnlyFans.

State investigators reported groups and accounts sharing child porn content to the company without effect, according to the filing.

"Our investigation into Meta's social media platforms demonstrates that they are not safe spaces for children but rather prime locations for predators to trade child pornography and solicit minors for sex," said Attorney General Torrez.

US law shields companies from liability for content posted on their platforms.

But the New Mexico lawsuit said the recommendations made by Meta's software meant it was not simply acting as a publisher.

Facebook and Instagram are not "simply presenting content created by others," the lawsuit said.

"Instead, Meta's algorithms operate to 'search and disseminate' sexually exploitative and explicit materials and to create its own social network of users looking to buy and sell the images and the children who are its casualties and its currency".

The lawsuit, filed in state court, said Meta had duped young users and their families about the safety of the platform, breaking laws that bar firms from deceptive practices, and created a product that is a hazard to public health and safety.

"In short, Meta has allowed Facebook and Instagram to become a marketplace for predators in search of children upon whom to prey," the lawsuit said.

The lawsuit personally names Facebook founder Mark Zuckerberg, saying he "called the shots" and had denied requests to make design tweaks or investments that would have improved child safety, while making misleading public statements about the issue.

"He promised publicly that he directed that Meta safeguard children, but privately demanded and delivered the opposite," the lawsuit said.

In a statement responding to the New Mexico allegations, the company said: "Child exploitation is a horrific crime and online predators are determined criminals."

"We use sophisticated technology, hire child safety experts, report content to the National Center for Missing and Exploited Children, and share information and tools with other companies and law enforcement, including state attorneys general, to help root out predators."

Meta is facing a mounting drumbeat of legal fights in the US over its treatment of its youngest users.

Those include a lawsuit filed by dozens of US states in October, which alleged that the company had contributed to a youth mental health crisis and misled the public about the risks of using social media.

Hundreds of families have also taken legal action, saying the platforms are harmful by design.

In the European Union, regulators this month also asked for more detail on the measures the firm had taken to protect children from abuse.

In June, in response to concerns about child exploitation on its platforms, Meta established a task force on the issue.

Since then, it said it had expanded the number of terms it polices and developed new technology to identify predators, among other steps.