The alleged action was alluded to last week by the Volunteer Fire Fighters Association - a separate group which reports to represent local members with complaints about treatment.
It stemmed from a house fire in Deniliquin on April 4, which RFS members were unable to attend.
The VFFA alleged the lack of attendance was linked to disputes some members have with senior management, but that has been refuted by the RFS, Mid Murray staff and local volunteer firefighters alike.
Mr Campbell also refuted the claims.
“Members of the RFS remain committed to supporting their local community,” Mr Campbell said.
“While work commitments and the rice harvest have affected the availability of some volunteers, our members are still responding to incidents in their local areas on a regular basis, just as they always have.
“Beyond just fires, RFS members respond to emergency incidents as needed across the community.
“The dedicated members of the RFS in the Mid Murray Zone, and right across the state, are the backbone of rural communities.
“The RFSA works closely with the RFS to build a strong service and enhanced member experience, particularly in supporting the code of conduct and ethics to protect all volunteers and staff.
“I want to reassure the community; they can have confidence that their local RFS continues to be driven by a desire to do whatever they can to help others.”