The union's elected leaders made the announcement Monday in an op-ed piece in the New York Times. They wrote, "This isn't the company we want to work for," adding that the "Alphabet Workers Union" aims to ensure that employees work at a fair wage, without fear of abuse, retaliation or discrimination.

The union's formation comes one month after the U.S. labor regulator accused the Alphabet unit of unlawfully monitoring and questioning several workers who were then fired for protesting against the company's policies and trying to form a union. The firings capped a two year battle between Google and its workers over the issue of how much input the rank and file has on which projects the company takes on and how it handles sexual misconduct and other workplace matters.

Google's director of people's operations said Monday, "Our employees have protected labor rights that we support. But as we've always done, we'll continue engaging directly with all our employees."

Alphabet shares fell in early trading Monday.