When it comes to the treatment of immigrants and refugees, Canada likes to project a rosy image.

But a new study entitled “Invisible Citizens: Canadian Children in Immigration Detention” from the University of Toronto’s Faculty of Law paints a grimmer picture.

Using internal documents from the Canada Border Services Agency, the study shows that an average of at least 48 Canadian children were housed in Toronto’s immigration detention centre each year between 2011 and 2015 because their non-Canadian parents were being detained.

“It feels like a prison,” Samer Muscati, director of the University of Toronto’s International Human Rights Program, said of the Toronto Immigration Holding Centre. "It has a concrete feel, with barbed wire all around you and bars on the windows."

Dozens more have been held at detention centres in Laval, Que. and Vancouver, B.C. Those records, however, are not public.

Like in prison, detained children are searched regularly and allowed outside for only one hour a day. According to the study’s author, Hanna Gros, a senior fellow with the University of Toronto’s International Human Rights Program, the impact on these kids can be tremendous.

“We’ve seen that children develop depression, anxiety,” Gros told CTV News. “They develop selective mutism.”

The alternative, splitting families and placing children in foster care, can be just as detrimental, experts say.

“We know from countries that use or over-use family detention to an extreme with horrific consequences, just what those consequences are," Michael Garcia Bochenek, senior counsel with the children’s rights division of Human Rights Watch, told CTV News.

An average of 242 non-Canadian children were also held each year between 2010 and 2014, including several teenage boys caught travelling alone who were then mostly placed in solitary confinement.

“In some cases it could go on for weeks or months,” Audrey Macklin, chair in human rights law at the University of Toronto, told CTV News. “It is very damaging to them."

For its part, the federal government says it is investing $138 million to upgrade and improve immigration detention centres like the one in Toronto.

"We're moving in the right direction,” Minister of Public Safety Ralph Goodale told reporters on Thursday. “My objective is to reduce the number of children in detention to virtually zero."

For that to happen, immigration lawyers say that the government would need to do away with birthright citizenship -- the practice of providing citizenship to any child born in Canada, regardless of their parents’ immigration status.

“Having a child in Canada is a positive factor for an avenue to permanent residency,” Calgary-based immigration lawyer Raj Sharma told CTV News.

While the government’s plan is to eventually remove children from detention centres, most immigration lawyers predict that numbers will actually increase this summer as warmer weather encourages more asylum seekers to illegally enter Canada from the United States.

With a report from CTV’s Peter Akman in Toronto