OTTAWA -- The federal government says it's trying to figure out how much its troubled electronic pay system has short-changed the unions representing thousands of civil servants facing pay problems.

But officials aren't saying whether the unions will be granted emergency payments like those being offered to workers who've been improperly paid through the Phoenix pay system.

One union, the Professional Institute of the Public Service of Canada (PIPSC), says it's owed nearly $2 million in unpaid dues from its members that have been collected by the government but not handed over, or not collected at all.

PIPSC president Debi Daviau says her union's focus has been on ensuring members are paid properly.

But she says the cash shortfall is creating serious problems in maintaining the resources needed to help civil servants sort through their pay issues.

PIPSC represents more than 50,000 federal employees, making it the second-largest federal civil service union.

The Public Service Alliance of Canada, which speaks on behalf of a majority of federal workers, won't say publicly how much it's owed, saying it will sort through the dues mess once it is satisfied the government has fixed the Phoenix problems for good.

The pay system has caused financial turmoil for up to 82,000 federal civil servants since it was launched more than a year ago. In some cases, government employees went without pay for months.