Putting two inmates in a prison cell designed for one person has "a minimal impact on the rates of violence in institutions," according to a report prepared by the commissioner of Correctional Service Canada.
CBC News obtained the document on double-bunking, written by corrections commissioner Don Head, after Public Safety Minister Steven Blaney mentioned it while testifying before a House of Commons committee last week.
"Correctional Services Canada has done some study that demonstrates that there's no link between double-bunking and violence in our facilities," the minister said.
Blaney told MPs that while most federally sentenced inmates have their own cell, "we feel that double-bunking is a normal practice, that actually prisoners are not entitled to their own cells."
The CSC briefing note dated Sept. 12, 2012, included findings that there has been a steady increase in double-bunking and security incidents since 2009, especially in the Prairie region. Double-bunking levels in the Prairie region more than doubled from 12 to 27 per cent in that time, and the rate of security incidents increased by 70 per cent over the same period.
But Head wrote that deeper analysis showed little connection between violence and overcrowding.
"The findings also suggest that double-bunking has little effect on violence between offenders housed in the same cell," he wrote.
Head also reported a strong relationship between violent incidents and the seizure of contraband materials in the Prairie region.
"It's a very short and I think superficial analysis of the situation," said Howard Sapers, Canada's Correctional Investigator.
Sapers, often also called the prisoners' ombudsman, told CBC News the paper too narrowly focused on incidents where an offender attacked a cellmate.
"The kinds of behaviours that we're seeing don't necessarily occur between cellmates but there are increases in these behaviours throughout the institution. So we do know there's a relationship between very crowded penitentiaries and increases in use of force, self-injury, in assaults," Sapers said.
Sapers agreed one cannot draw a straight line between violence and double-bunking because there are numerous consequences to prison overcrowding, such as a scarcity of escorts for inmates on work release, prison psychologists, teachers and programs offering offenders the opportunity to do something meaningful beyond spending time in a cell.
Jason Godin, national vice-president of the Union of Canadian Correctional Officers concurred.
"There's lots of contributing factors, but the bottom line is when you start to overcrowd institutions, it's a breeding ground for more violence and more crime."
Averaged out across Canada, 20 per cent of inmates are double bunked, according to CSC.
Godin said double-bunking is much higher in Ontario and across the Prairies, hitting as high as 80 per cent at the maximum-security institution in Edmonton, where guards have reported a steady rise in violence.
CSC refused CBC News' request for an interview, but the briefing note went on to say the department has started more in-depth research to pinpoint what is triggering more violence in Canada's penitentiaries.