The actual statement is the following from ‘Inside the Third Reich’, p304:‘Of all the urgent questions that weighed upon me during my early weeks in office, solution of the labor problem was the most pressing. Late one evening in the middle of March, i inspected one of the leading Berlin armaments plants, Rheinmetall-Borsig, and found its workshops filled with valuable machinery, but unused. There were not enough workers to man a second shift. Similar conditions prevailed in other factories.’
The reason for the manpower shortage was that there was also demand from the armed forces. The same person could not be at the front and in the factory.The Germans tried to solve this problem by using forced and slave labor.