Women have been brought into the State and housed against their will for sexual exploitation, the Joint Committee on Justice, Equality, Defence and Women's Rights has heard.
Gardai investigated one such case reported last July and a file has been sent to the Director of Public Prosecution, Ms Caoimhe de Bara, campaigns officer with Trocaire, said.
Trocaire became aware of other cases through groups working on the streets to combat exploitation, she added.
When sexual exploitation occurred, people were brought into the State and kept in "closed" houses which functioned as brothels, she said. Often the women had not applied for asylum and so their existence in the State was not known to the authorities. The women's papers and passports were taken from them by those who brought them in, Ms de Bara said.
People who were brought into the State through trafficking should not be treated as criminals but as victims, she said. They were witnesses to a dangerous crime and needed to be protected.
In some cases they should be allowed to stay in the country they had been brought into rather than being deported. If deported they could be under threat from the mafia groups involved in trafficking in their home countries, Ms de Bara added.
Sexual exploitation occurred on a greater scale in the Netherlands and Belgium where young women from Nigeria were forced into prostitution, said Ms Muireann O Briain, director of ECPAT (End Child Prostitution Child Pornography and Trafficking of Children for Sexual Purposes).
Contracts were signed in villages in Nigeria for work in Europe but on arrival the women were locked up and exploited. "Some of the women have become mentally deranged because of the coercion," Ms O Briain said.
Research showed street children in Dublin, Dundalk and Waterford were also being exploited, she added.
Ms O Briain urged the committee to examine the risk to children from the Internet where children can be exploited by paedophiles.