The Union of Canadian Correctional Officers says prison guards are on the frontline of having to deal with the effects of Harper's tough on crime agenda.
Critics say the government's move to tougher sentences for some offences will cause a boom in the inmate population.
Many guards cheered as national president Pierre Mallette stood on top of a bus and complained that overcrowding and double-bunking is leading to increased prison violence.
Mallette says the union has been trying repeatedly to meet with Public Safety Minister Vic Toews, but hasn't had any success.
Toews noted in July that the number of people behind bars was 3,000 fewer than what the Correctional Service of Canada had predicted for this year.
Officials, however, have pointed out the number of people behind bars is still growing.
"It's getting grim and it's getting grimmer by the day," said Kevin Grabowsky, the union's regional president for the Prairies.
Grabowsky said the Prairies has the highest number of double-bunked prisoners, and he said that close to a third of prisoners are coming into jail as gang members. He said that means anyone who isn't a gang member is pressured to join one.
Without an increase in rehabilitation and other services, Grabowsky said the guards' goal of trying to produce inmates who won't return to jail is jeopardized.
The rally was part of a national tour Mallette has been making of the 52 federal penitentiaries across Canada. He said the union planned to distribute postcards in Harper's constituency and would continue to target Conservative MPs to make sure their constituents understand what is happening.
The government has maintained that its crime legislation will keep dangerous and repeat offenders behind bars.
It announced earlier this year it is shutting down two older prisons — Kingston Penitentiary in Ontario and the Leclerc prison north of Montreal — and scrapping any plans to build new facilities. Instead, it has promised to add 2,700 new beds to existing facilities to ease over-crowding.
Grabowsky said those new beds aren't here, yet.
"We're generally in a place right now where it's getting dangerous for officers," he said.
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