TORONTO -- Chronic overcrowding and understaffing have pushed tensions in Ontario's prisons to a boiling point, the union representing the province's correctional officers said Thursday in defending itself against a damning report on jailhouse brutality.

The Ontario Public Service Employees Union said last week's report by the provincial ombudsman paints a one-sided picture of what actually happens in prisons and jails -- a marked departure from its initial reaction.

The union originally welcomed the report and its recommendations, saying it had long told the Ministry of Community Safety and Correctional Service to "deal with problem staff."

After meeting with representatives from the province's 29 facilities Thursday, the union said ombudsman Andre Marin chose to point the finger at guards rather than investigate what it calls the growing culture of violence in these institutions.

"The level of violence in the workplace is the issue the ombudsman should be looking at," union spokesman Dan Sidsworth said at a news conference.

"What is causing all this violence in our workplace? And we're saying it's these other issues, it's the shortage of staff, it's the overcrowding, it's the lack of equipment and the lack of training."

In his 135-page report, Marin said some jail guards are brutalizing inmates and covering up the abuse by destroying or falsifying records and intimidating colleagues.

Filled with disturbing pictures and stories, the document outlined a grim reality in the province's correctional facilities, saying guards could punch, slap, kick, or stomp on inmates -- often with complete impunity because their fellow officers don't speak up.

But Marin was careful to blame a "rogue minority" of correctional officers who bully inmates and colleagues, and acknowledged that overcrowding and understaffing exacerbate simmering hostilities.

Two summers ago, the ministry began a review of more than 3,500 files involving alleged excessive use of force and investigated 55 cases. The probe confirmed brutality in 26 of those cases.

The union's combative response "tells me that the code of silence is entrenched just as much as I thought a week ago when we released the report," Marin said Thursday.

"It's important not to pretend that there's no problem, that's how I see the union's position today and I'm very sad," he said.

Many of the recommendations laid out in the report -- including those for more resources and training -- echoed the union's own demands, which should have earned guards' support, he added.

Instead, it has left them feeling "disillusioned," said Clark Moss, who works at the Central East Correctional Centre in Lindsay, northwest of Peterborough.

In the past two years, roughly 900 correctional officers have been assaulted on the job, "but you don't see the ombudsman publicizing pictures of my officers with their chest ripped open from bites and these types of activities that go on," he said.

Among the problems highlighted by the union was the lack of protection for guards, who can only use equipment such as pepper spray and knife-proof vests when escorting inmates into the community.

"When we walk in, I have my hands, and I have a pen, and I've got a radio, and I've got to hope that people come help me," Moss said.

The union said that in focusing on rare occurrences of brutality against inmates, Marin ignored the far more common cases of inmates beating each other or attacking guards.

"The excessive use of force is not systemic," Sidsworth said. "What is a systemic problem is chronic understaffing."

The government, meanwhile, repeated its assurances that it has already begun taking action.

"We understand the concerns of the union and we're working closely with them to resolve these issues," a spokesman for Corrections Minister Madeleine Meilleur said in an email.