computer typing is a classified ad website branded an "online brothel" by authorities Glenn Carstens-Peters/Unsplash

Missouri's top law enforcement official on Tuesday (2 August) asked a court to dismiss a lawsuit that seeks to stop him from investigating the company, calling it "totally frivolous."

Backpage sued attorney general Josh Hawley last month over his investigation, arguing federal law and the First Amendment bar claims against the Dallas-headquartered website, which hosts classified ads from around the world.

Hawley's office filed a motion to dismiss the lawsuit, saying it has evidence undermining Backpage's claim that it doesn't play a role in the sex-related ads posted on its website and that Hawley should be allowed to continue investigating.

Hawley's office is investigating the company for potential violations of the Missouri Merchandising Practices Act, which prohibits deceptive or misrepresentative business practices.

"My message to Backpage is: the truth is coming for them. The truth is coming out," Hawley told the Associated Press. "I will not be bullied to stop this investigation."

An attorney for Backpage declined to comment. has long been labelled by authorities as an online brothel. A recent US Senate report released in January contends that the site is involved in 73% of all child trafficking reports that the National Centre for Missing and Exploited Children receives from the public.

The report, by the Senate's Permanent Subcommittee on Investigations, charged that Backpage has created a lucrative marketplace that makes child sex trafficking easier.

It cites internal documents showing that up to 80% of the site's ads are edited to conceal the true nature of the underlying transaction. Backpage denied the allegations.

Backpage argues that it doesn't control the sex-related ads and is protected by the Constitution and the federal Communications Decency Act, which grants immunity to websites that host content created by others. Various court rulings have upheld Backpage's defence claims.

The company has also said that it takes efforts to prevent illegal activity with warnings and filters that block and remove improper ads.

Hawley's court motion to dismiss the Backpage suit against him cites claims made in the US Senate report and by several news outlets that documents seem to show that a Philippines-based contractor, Avion, solicited and created sex-related ads for Backpage customers overseas.

Audio recording obtained

Court documents filed Tuesday show Hawley's office also has an audio recording of a phone call that an Avion employee made to a woman who allegedly posted a sex-trafficking ad on another website in which the employee tried to give her information about posting an ad on Backpage for free.

Hawley's office declined to say which country the woman lived in, so it's unclear whether the call might have broken any laws. Sex work is legal in some countries.

Also Tuesday, a group of federal lawmakers, including Democratic senator Claire McCaskill, of Missouri, filed legislation that McCaskill said would strip protections from the Communications Decency Act for companies including Backpage, which she said "has tried to enjoy for its conduct in connection with trafficking people for sexual activity, including children".

'Frivolous and unpredictable'

McCaskill, who served on a Senate subcommittee that investigated Backpage, said the bill is narrowly tailored so that it would only affect sites that "knowingly participate in placing any information on their sites that facilitates trafficking, or if they recklessly do it if they're getting paid for advertising".

The Internet Association, which counts Google, Facebook and Amazon among its members, opposes the bill. The industry group's president and CEO, Michael Beckerman, issued a statement suggesting that the bill could create a "new wave of frivolous and unpredictable actions against legitimate companies rather than addressing underlying criminal behaviour."

"The bill also jeopardises bedrock principles of a free and open internet, with serious economic and speech implications well beyond its intended scope," Beckerman said.