The president of a major labor union sent a blistering letter to its members on Wednesday calling out other unions, dubbing them “bottom-feeding organizations” for their opposition to a controversial oil pipeline project.

There are more than 1,100 members of the Laborers International Union of North America (LIUNA) working construction jobs on the Dakota Access pipeline, wrote Terry O’Sullivan, the union’s president.

The pipeline has drawn opposition from environmentalists and Native American tribes in North Dakota, and intense, occasionally violent protests from left-wing anti-energy activists that O’Sullivan derided as “THUGS.” 

However, he reserved his most pointed criticism for a group of labor unions that have publicly backed those activists and the larger anti-pipeline environmental movement.

“They are a group of bottom-feeding organizations that are once again trying to destroy our members’ jobs,” O’Sullivan wrote.

He called out five “job-killing” unions by name: the Communications Workers of America (CWA), National Nurses United (NNU), the Amalgamated Transit Union (ATU), the American Postal Workers Union (APWU), and the Service Employees International Union (SEIU).

“LIUNA will not forget the reprehensible actions and statements against our members and their families from the five unions listed above,” O’Sullivan wrote. 

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