Justice chiefs are running a seriously flawed system for identifying victims of human trafficking, rights campaigners have warned.
The Immigrant Council of Ireland issued the warning as it revealed hundreds of young women from Latvia, Estonia and Lithuania, often poor and not well educated, were brought by gangs to Ireland from 2009 to wed mainly Asian men in sham marriages.
It said it was particularly concerned about the numbers who were raped after being brought here, and the numbers who were highly vulnerable, with some having mental health difficulties.
Brian Killoran, chief executive of the Immigrant Council of Ireland, hit out at lawmakers for not defining the women as victims of human trafficking.
He said there were strong indicators that the prospective paid-for brides had been trafficked, including "a highly organised system of targeting, recruiting and exploiting vulnerable young women".
"There is also evidence of deception and control; movement across borders; appalling experiences of physical and psychological abuse; and incidents of rape, sexual abuse and enforced domestic servitude," he said.
In 2014 gardai began Operation Vantage, which found a clear pattern of men from the Indian sub-continent marrying in Ireland to women from Eastern Europe - mainly Latvia, Romania, Hungary and Estonia, and also Portugal.
The Immigrant Council of Ireland described the problem as pervasive.
Marriage data revealed more than 1,600 marriages were registered in Ireland between Latvians and third country nationals since 2004.
Since 2006 about 2000 people not from Ireland or Latvia applied for a residence permit as a family member of an EU national, based on a marriage with a Latvian citizen.
Estonia records about 45 to 50 of its citizens getting married in Ireland each year to people from a third country, often Asians.
The Immigrant Council of Ireland report found diplomatic staff in the Baltic states raised concerns about sham marriages with justice chiefs in Ireland to "little effect" and found themselves faced with "negative and unhelpful responses".
It said the Latvian embassy reported 233 potential human trafficking victims in Ireland from 2011 to 2014 but Irish authorities did not identify any victims of trafficking within the context of a sham marriage at that time.
Mr Killoran said: "At the centre of this phenomenon are international criminal gangs, with sophisticated networks to transport people across borders in a very systematic way.
"Addressing this issue will require bilateral, police and NGO cooperation between origin states and Ireland, and effective law-enforcement responses and measures to prevent exploitation."
The Immigrant Council of Ireland said the system for identifying human trafficking victims in Ireland is seriously flawed.
It said NGOs have been at the forefront of responding to the needs of all victims of trafficking, "and the case of women subjected to exploitative sham marriage is no different".
"The failure of the authorities to formally identify these women, as well as other EU citizens and asylum seekers, as victims of trafficking crimes, and to provide appropriate safe accommodation, especially for victims of sexual violations, continues to frustrate their efforts to deliver best practice responses," the report said.
The Department of Justice said the report was "somewhat outdated" as it dealt with the legal position up to the end of 2015.
It said there have been " significant measures" to address this issue, including new powers from August last year for officials in the civil registration service to refuse a licence if a couple is suspected of attempting a sham marriage.
It said 63 people have been arrested under Operation Vantage and they have been either charged, prosecuted or removed from Ireland and that gardai estimate sham marriages have been reduced by 75%.