A US judge in New Mexico ordered that $420m (£312m/€364) of the sum be spent on treatment services for young people, with the remainder allocated to awareness and prevention, screening services and other costs over the next five years.

The penalty comes on top of $375m (£280m/€325) in damages that Meta was ordered to pay after a jury found in March that the company had knowingly harmed children’s mental health, bringing the total to $942m (£700m/€817).

Meta has said it disagrees with both rulings and will appeal.

New Mexico attorney general Raul Torrez described the decision as “a victory for every parent who has worried about what social media is doing to their child and every child who deserves to grow up safer online”.

Meta is facing lawsuits from thousands of families over similar allegations. Earlier this year, it and Google were found liable by a Los Angeles court for a woman’s social media addiction in a ruling described as a landmark.

In a statement, Meta said: “We work hard to keep people safe on our platforms and have been transparent about the challenges of identifying and removing bad actors and harmful content.

“We remain confident in our record of protecting teens online and will continue to defend ourselves against claims that misrepresent the facts.”

Judge Bryan Biedscheid, who said Meta had created a “public nuisance”, also ordered Facebook and Instagram to display information about protection features, best practices and tools for addressing inappropriate comments.

He said Meta should continue improving its age-assurance systems, including AI tools used to determine users’ ages, and develop an “under-13-years-of-age prediction model” within two years. Any changes would be subject to review by New Mexico.

Another trial against Meta is due to begin in California later this month, involving four of the 29 states suing the company in federal proceedings over allegations that it knowingly designed addictive features targeting children.