The amendment comes from the Labour party who want the government to allow in 3,000 children in addition to the 20,000 refugees that will enter the UK over the next five years.
Under current plans, the UK would only take in migrants from camps in the Middle East and North Africa.
- UK pledged to take in 20,000 Syrian refugees
- Families to arrive over five years
- Some families already being re-settled
Dave Smith from the Boaz Trust, a Christian organisation serving asylum seekers in Greater Manchester, told Premier's News Hour thousands of children are unaccounted for.
He said: "We know that 10,000 children under 18 have gone missing and Europe, and they've come from Syria and Afghanistan and places like that.
"You can only assume that some of them have ended up in trafficking gangs for sexual exploitation and other things like that."
Dave Smith told Premier that vulnerable children are a target for traffickers: "If you've been without your parents, if they've been killed, you're extremely vulnerable, and if people promise you something you'll probably go with them.
"Then you find out it's something else.
"That's the way trafficking works, and if weren't not protecting these children then we share some of the blame."
'The Jungle' refugee camp in Calais, France
It is thought at least a dozen Tory MPs could back Labour calls for the UK to take in 3,000 lone children who are already in Europe.
The UK government says its scheme will target unaccompanied children in the Middle East and North Africa, as well as those considered at risk of abuse and exploitation, such as children threatened with child labour and child marriage.
The result of the vote will not be known until late Monday evening.
Listen to Premier's Alex Williams speak to Dave Smith here:
