According to a report in The Times on Friday, a UN migration agency criticised the company for allowing people traffickers to use its site to "advertise their services, entice vulnerable people on the move and then exploit them and their families".
"It is irresponsible for tech companies like Facebook to ignore this issue. It's hard to believe that the tech giants cannot put some real effort into stopping these smugglers from using their platforms for racketeering," Mohammed Abdiker, of the International Organisation for Migration, was quoted as saying.
According to Facebook, people smuggling is illegal and any posts, pages or groups that co-ordinate this activity are not allowed on its platform.
"We encourage people to keep using our reporting tools to flag this kind of behaviour so it can be reviewed and swiftly removed by our global team of experts, who work with law enforcement agencies around the world," Facebook said.
This is not the first time the social media giant has faced a content-related scandal.
Earlier this year, Facebook was surrounded in criticism for not doing enough to block the video related to suicides, murders, terrorism and rapes broadcast through its live-streaming service.
In Europe, Facebook is under pressure to speed up its process to block the hate speech content or face fines from the legislators.
Facebook announced in May it would hire an additional 3,000 staff for its content moderation team, expanding its strength to 7,500 members.