CALGARY - A union representing prison guards rallied in front of Prime Minister Stephen Harper's Calgary constituency office Saturday to complain about Conservatives' crime policies.

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.