Apparently "the left-communist German Workers Union Unitary-Organisation (AAUD-E)" had (deliberative) delegates at the founding of the IWA in Berlin in 1922.* I know some councillists (specifically Otto Ruhle) advocated revolutionary unions, but didn't know "left-communist unions" had ever actually existed. Anyone know any more?
* V.Damier (2009), Anarcho-syndicalism in the 20th century, Black Cat Press, Edmonton; p.82.



I think the AAUD had over 100,000 members at one point. It was linked to the KAPD.
The AAUD-E, of which Otto Rühle was the leading light, were probably better described as council communists as they had broken with the idea that a communist party was needed.