Spreckels had an often-contentious relationship with other powerful business figures and interests, both in the United States and in the Kingdom of Hawaii. This was reflected in frequent negative publicity for Spreckels, particularly in the often yellow press that characterized much of American journalism of that era.^[1][2] One such rivalry would grow into a family enmity between Claus Spreckels and his sons and Charles and M. H. de Young, owners of the San Francisco Chronicle, culminating in the attempted assassination of M. H. de Young by Adolph B. Spreckels in 1884.^[2][3][4] Allegations by the Chronicle and other critics included the claim that he practiced slavery on his Hawaiian plantations, that he acted as a pimp for King Kalākaua, and that he had defrauded stockholders in his company.^[2]

Like other owners of sugar plantations in Hawaii prior to American annexation, Spreckels employed laborers on the contract labor system,^[5][6] a system having some features of indentured servitude, in which an immigrant laborer contracted to work for a single employer for a set period (typically 3-5 years) for a low wage as repayment for the cost of passage to Hawaii.^[7] Spreckels was a strong advocate for continuation of this system, arguing that sugar could not be produced economically without a reliable supply of cheap labor.^[5][6] This led him to oppose the annexation of Hawaii by the United States, something that was supported by many powerful Americans in Hawaii, as the use of contract labor was illegal in the United States under the 1885 Alien Contract Labor Law and other laws.^[5][8]

In the 1880s, the Chronicle began running articles alleging that the laborers on Spreckels plantations were effectively enslaved, that his plantations engaged in unacceptable labor practices, and that the living conditions of the laborers were inhumane, with some particularly inflammatory articles finding their way into the national press.^[1][9] The majority of San Francisco newspapers of the era, however, did not endorse the Chronicle's reporting on the issue, claiming that the labor conditions on Spreckels plantations were acceptable and, in fact, much better than those on sugar plantations in the Caribbean, a position later supported by independent investigations by the Portuguese and Norwegian governments.^[9]

Negative publicity about Spreckels Hawaiian operations continued to follow him even after the divestment of his Hawaiian operations in 1893. In 1900, an incident took place in which 114 Puerto Rican migrant laborers were transported to Hawaii under coercive and inhumane conditions. News of the plight of these laborers as they were being transported to California for shipment to Hawaii became a cause célèbre in the American press, particularly in San Francisco. The laborers were recruited and trafficked by labor agents who, according to most accounts, were hired by the Hawaiian Sugar Planters' Association,^{[10][11][12][13][14][15]} though other stories linked the agents to Claus Spreckels.^{[2][16][17][18]} John D. Spreckels issued a statement via his newspaper, the San Francisco Call denying that neither he nor Claus Spreckels had anything to do with the recruitment of these laborers.^[16]