The four companies that have expressed an interest in multibillion-dollar government contracts for detention centres on Manus Island and Nauru should be aware of the reputational harm  of being associated with policies of cruelty and harm.

A Senate estimates question on notice from Australian Greens Immigration spokesperson Nick McKim revealed Serco, Decmil Services, Canstruct and Ostwald Bros have expressed interest in taking over the major contract for Australia's offshore detention centres.