The International Labour Organisation estimates that the industry is worth around £20bn, and the global day aims to raise awareness about the issue.
Amy Jasper, from Stop the Traffick, told Premier this is not just a problem happening overseas: "It is happening here behind closed doors in residential properties, in factories, on farms, here in this country.
"That's something we all have a responsibility to know how to spot the signs and know what to do and who to report it to if we think we've seen something suspicious."
She said there are many signs to look out for that can suggest someone is in a vulnerable situation: "Is there people who're being moved around at odd times of day from different residential properties, are there strange people picking up children at the school gates or who aren't related to them who might be grooming people or giving teenagers gifts, phones or money in exchange for sexual favours or being trafficked around?
"Do they have their passports or documentation on them to say who they are? Have they been threatened or been told that their family members of themselves might be hurt or killed by someone? There's quite a few things to look out for."
Listen to Premier's Hannah Tooley speak to Amy Jepson here:
