The Professional Association of Foreign Service Officers, which includes more than 600 Canadian diplomats in overseas missions, has been without a contract since mid-2011 and wants pay equity with other public servants.
The union wants to force Treasury Board back to the bargaining table, so it can address a core grievance — that its members are paid $10,000 to $14,000 less than their counterparts who do similar work in other federal departments.
Timothy Edwards, the union's president, said the work-to-rule measures will start small but could evolve into a strike.
"We are looking at the full range of job action measures, so up to and including actual withdrawal of service or striking," Edwards said.
Andrea Mandel-Campbell, a spokeswoman for Treasury Board Secretary Tony Clement, said it's the government's position that a strike would be unfortunate.
"The foreign service is a highly sought after and well-paid posting," Mandel-Campbell said. "The government will continue to bargain with PAFSO in good faith to reach a reasonable settlement that is fair to workers and taxpayers."
The potential labour unrest comes as Canada tries to finalize a free-trade deal with Europe and seeks to expand markets in Asia and the Middle East.
The union has been without a contract since June 2011. Edwards said negotiations with Treasury Board ended in late January.
He said the major obstacle for the union is the fact that foreign service officers are paid less for the same work performed by other public servants both inside the Foreign Affairs Department and other federal departments.
"In some cases, these workers make as much as $10,000 more than us, even though they don't face the same challenges that we do," said a note posted on the union's website on Tuesday announcing that it was in strike position.
"Our families must regularly move homes, our children must constantly change schools, our spouses must quit their jobs, we risk our safety and health in hazardous environments, and we miss countless birthdays and other special moments with friends and family while living for months or years at a time in war zones and disaster areas."
Edwards said the union has done its part by agreeing to the government's proposal of a 1.5 per cent wage increase.
He said the wage gaps have lingered for the last eight years, before the most recent recession, adding that the union's members are prepared to do their part in tough economic times.
"All we're looking to do is catch up to what other occupational groups have already been given in collective bargaining."
Asked to comment on the wage gap issue, Mandel-Campbell would only reiterate that the foreign service "is a highly sought after and well paid posting."