"The detention and use of women and girls as workers without pay would amount to ‘forced labour’ under the 1930 Forced Labour Convention of the International Labour Organisation, which Ireland signed in 1931. It appears from the reports provided by these women and girls that their treatment constituted slavery," he said.
Mr Shannon said the treatment of the women in the laundries fitted the convention’s definition of slavery as including forced or compulsory labour.
"It is clear that the testimonies of the survivors indicate that their treatment fits this definition: they were sent to institutions, in which women and girls were made to work without pay, where physical punishment was practiced, doors were locked and escapees were likely to be returned by the police."
Mr Shannon also said the need to deal with the matter of accountability and redress was crucial to ensure Ireland’s compliance with international human rights laws. He also said the right to redress and remedy still existed even where the State was not directly "overseeing slavery".
Justice For Magdalenes PRO Claire McGettrick said the intervention of Mr Shannon was "especially welcome" given that the majority of survivors in contact with the group were children when they were incarcerated in the laundries.
"JFM recently obtained testimony from a woman who was employed as a ‘paid hand’ at the Sisters of Mercy Laundry in Galway.
"This woman offered vivid accounts of the terror experienced by children in Galway — particularly poignant are her descriptions of young girls who clutched each other in fear when they arrived at the laundry, having been transferred from Ennis Industrial School," she said.
JFM advisory committee member and director of Women’s Studies at UCD’s School of Social Justice Dr Katherine O’Donnell, also welcomed comments by Archbishop Diarmuid Martin that "research-based investigation" might better address such issues as the Magdalene Laundries, pointing out it has been carrying out such research since its foundation.
JFM has, to date, uncovered over 50 clear examples of the State committing girls as young as 14 years old to Magdalene Laundries.
The group has provided over 500 pages of newly- gathered survivor testimony to the Senator Martin McAleese led inter-departmental committee examining State involvement in the Magdalene Laundries.
The question of such involvement has already caused Justice Minister Alan Shatter to backtrack on the issue in recent months.
While in opposition, he said there was "irrefutable evidence" of such collusion through court records and files held by the Department of Justice.
However, Mr Shatter has since rowed back on such comments claiming the issue had a "very complicated" background that did not have a "simple, straight-forward explanation".