An estimated 500 correctional officers marched towards Stephen Harper's office in southwest Calgary.

The guards claim their jobs are getting more dangerous because the country's 52 prisons are overcrowded and some inmates are posing a threat to their safety.

The rally was designed to raise public awareness about the impact of federal policy on public safety, but the prime minister's office has suggested the protest is a stunt.

The federal prison population has swelled to 14,419 from 12,671 five years ago.

According to figures provided by the Correctional Service of Canada, the percentage of prisoners double bunked has climbed to 17.4 per cent nationally, up from 9.6 per cent five years ago.