The United States National Labor Relations Board (NLRB) has discovered that Activision Blizzard withheld pay rises from staff at Raven Software's QA department.

According to The Washington Post, the organisation believes that this is due to these workers being in the process of unionising. In April of this year, QA testers at Raven were given pay rises, except for those forming a union.

In the wake of this discovery, Activision Blizzard and the Raven Software union – Game Workers Alliance – are continuing negotiations, though if they are unable to come to an agreement, the NLRB could get involved.

“Due to legal obligations under the [National Labor Relations Act] requiring employers not to grant wage increases while an election was pending, we could not institute new pay initiatives at Raven because they would be brand new kinds of compensation changes, which had not been planned beforehand," Activision Blizzard spokesperson Rich George said.

"This rule that employers should not grant these kinds of wage increases has been the law for many years.”

The Raven Software union was brought into existence earlier this year and was approved by the NLRB in April.