WASHINGTON (Reuters) -Membership in the United Auto Workers union fell 3.3% in 2023 to 370,000, its lowest level since 2009, according to a report filed on Friday with the U.S. Labor Department.

The UAW is "clear-eyed that our union and many of our industries have been going in the wrong direction for years," a union spokesperson said, adding that is "why we've made a historic commitment to organizing the rest of the auto industry, tens of thousands of higher education workers, and everyone in our core industries from heavy truck to agricultural implements to aerospace."

After winning record new contracts with General Motors Ford and Stellantis ( STLA ), the UAW launched a first-of-its-kind campaign to organize the entire non-union auto assembly sector in the U.S., initiating simultaneous organizing efforts at non-union operations owned by Volkswagen, Toyota ( TM ), Mercedes-Benz, Hyundai and other automakers.

UAW membership is down from 397,000 at the end of 2020 and from its 1970 high of 1.5 million members. It fell to 355,000 in 2009 during the Great Recession and the U.S. auto sector restructuring.

Next month, the UAW's organizing effort gets a big test when workers at Volkswagen's Chattanooga, Tennessee, assembly plant will vote April 17-19 on whether to join the union.

Pablo Di Si, head of Volkswagen's North American business, told Reuters this week the company will remain neutral ahead of the organizing vote. "Being neutral does not mean being silent," he said, saying the company would correct misinformation so employees can have the facts "and make their own decision."

For more than two decades, the UAW has tried and failed to organize non-union U.S. auto assembly plants established by Asian and European automakers, mostly in southern states with laws and political leaders that are hostile to unions. The UAW has lost two votes at VW's Tennessee plant since 2014.

Winning a vote to organize the plant would be a significant milestone for the union in an election year where both U.S. President Joe Biden and his presumptive Republican rival Donald Trump are aggressively courting votes from UAW members in Michigan and other industrial swing states.