OTTAWA — Federal government workers have the constitutional right to participate in election campaigns, but many hold back for fear of retribution.

Rules allow civil servants to freely take part in political activities, as long as they are done outside work hours and don't disparage their political bosses. Some refrain because they worry about limited career growth or other repercussions.

"I think it's safe to say that (Stephen) Harper's style of government has certainly put a chill on public sector workers actively engaging in campaign-related activities," says Patty Ducharme, national vice-president of the Public Service Alliance of Canada. "He has shown himself to be quite vindictive with people who have spoken out on issues."

Ducharme said the union is encouraging its 172,000 members across the country to get involved in the campaign, be aware of issues and support progressive candidates who support public services and jobs. But they are warned not to cross the line by using government equipment and vehicles or wearing work uniforms when knocking on doors or driving in lawn signs.

The union does not officially endorse any political party.

"Common sense enters into this, and we recognize the Public Service Commission is fairly conservative when it comes to the application of the guidelines. We think sometimes they're overly cautious," Ducharme said, adding the union would back any member who faced ramifications for appropriately engaging in the campaign.

Relations between the employer and civil servants have been strained since the Conservatives came to power in 2006, escalating into high-profile battles waged by the federal government against top civil servants such as former Nuclear Safety Commission president Linda Keen and ex-Statistics Canada chief Munir Sheikh.

Ducharme said the Conservative government has a pattern of shifting policy or practice on the fly, then hanging public sector workers "out to dry" when there's negative public reaction.

Claude Poirier, president of the Canadian Association of Professional Employees, said many senior-level bureaucrats refrain from engaging in political campaigns over concern about limited professional advancement.

"It's probably part peer pressure and rumours and gut feelings," he said. "It's not based on letters that people would have received or based on pure fact, but it's the kind of thing you get to know. It's like overtime. You know if you want to be promoted to a management position, if you keep asking for overtime you might impair your capacity for getting that promotion."

The association's 14,000 members work in senior professional roles, such as economists, policy analysts, translators and statisticians. Some work in key departments such as Treasury Board, the Privy Council Office or Finance.

"Political activities are not particularly welcome in those departments because of the central role played by these organizations in the federal government," he said.

While some Conservatives have accused the civil service of having a Liberal bias, Poirier said members represent the spectrum of political views — from the extreme left to the extreme right.

The Conservative party campaign declined to comment.