Facebookhas been named as the target of a new competition probe launched by nine US attorneys general, the latest in an ever-increasing legion of regulatory actions against the social media giant.

A bipartisan coalition comprising eight US states and the city of Washington DC said on Friday that it would use "every investigative tool at [its] disposal" to investigate whether Facebook has stifled competition or put users at risk.

The effort, led by New York's attorney general Letitia James, will focus on Facebook's dominance of the social media market, which it controls a large share of through its ownership of Instagram and WhatsApp.

It comes as another coalition of US states, led by Texas, prepares to investigate Google's impact on the digital advertising market, while the federal justice department pursues a separate "top-to-bottom" probe of Google, Amazon, Facebook and Apple.

“Even the largest social media platform in the world must follow the law and respect consumers," said Ms James. "I am proud to be leading a bipartisan coalition of attorneys general in investigating whether Facebook has stifled competition and put users at risk.

"We will use every investigative tool at our disposal to determine whether Facebook’s actions may have endangered consumer data, reduced the quality of consumers’ choices, or increased the price of advertising.”