A bipartisan group of 20 senators led by Sen. Rob Portman, R-Ohio, introduced legislation on Tuesday aimed at making sure websites that facilitate sex trafficking can be held liable for their role by both victims and state officials.

The bill is a response to Backpage, which the senators have concluded plays a role in sex trafficking and should be held liable for the knowing online sex trafficking activity on its site.

"Stopping sex trafficking is one of the greatest humanitarian and human rights causes of the 21st century," Portman said in a statement. "Our bipartisan investigation showed that Backpage knowingly facilitated sex trafficking on its website to increase its own profits, all at the expense of vulnerable women and young girls."

A two-year investigation into the matter led by Portman and Sen. Claire McCaskill, D-Mo., resulted in a report titled "Backpage.com's Knowing Facilitation of Online Sex Trafficking," which revealed that the website knew about sex trafficking happening on its site but covered it up to increase profit. The Stop Enabling Sex Traffickers Act introduced on Tuesday is a result of that investigation.

The bill would amend the Communications Decency Act to allow victims of sex trafficking to seek justice against websites that facilitated the crimes against them. It would also remove federal liability protections for websites involved in violating federal sex trafficking laws, and let state officials take against these sites.

"It is disgraceful that the law as written has protected Backpage from being held liable for enabling these horrific crimes," said Sen. John McCain, who co-sponsored the bill. "Our legislation would eliminate these legal protections and ensure companies like Backpage are brought to justice for violating the rights of the most innocent among us."