Alberta's largest public service union has officially asked the province to change how it defines a spouse in its benefits package for government employees.

According to the "My Choice" package distributed to workers in spring 2008, a "spouse" is someone of the opposite sex. People in same-sex marriages are called "benefit partners," even though same-sex marriages have been legal in Alberta since July 2005.

On Tuesday, the Alberta Union of Provincial Employees (AUPE) told the province's Corporate Human Resources Department that they want the wording changed to remove any reference to gender in the definition of a spouse and to retain the term "benefit partners" for anyone in a common-law relationship.

The government is harming its own employees by not recognizing that people in legal same-sex marriages are spouses, David Climenhaga, communications director for AUPE, said Wednesday.

"It contributes to an atmosphere of discrimination. It contributes to justifying treating people in different ways," Climenhaga said.

Climenhaga admits the union did not object to the way spouse was defined when the benefits package was first drafted, because the priority at the time was to ensure there would be equal coverage for everyone.

The government has defended the difference in definitions by saying the coverage is the same for "spouses" and "benefit partners."

But Alberta Liberal Leader David Swann challenged Premier Ed Stelmach on the issue in Wednesday afternoon's question period.

"Why does the premier's government continue to use outdated and dismissive terms instead of the real term spouse?" Swann asked.

"The benefits are the same. They're all treated fairly and that's the most important thing," Stelmach said.

The wording in the benefits package was first raised by former government employee Scott Mair in a story CBC News first aired on Monday.

Mair ended up quitting his job several months after he received the booklet because he felt he was being treated differently because he was married to a man, he said.

With files from John Archer