Joe McCloskey died after falling through a roof into a blazing storeroom at Gorteen House Hotel in Limavady on Halloween 2003.
The father-of-five and a colleague had earlier been ordered onto the roof of the burning building.
In 2017, former health minister Michelle O’Neill ordered a review into the 50-year-old’s death.
The review concluded there were lessons to be learned in relation to the support provided to the McCloskey family by the Northern Ireland Fire and Rescue Service (NIFRS) and Northern Ireland Fire Brigade and the “efficacy of the internal investigation”.
The report made recommendations including that the NIFRS apologise to the McCloskey family for failing to learn from previous experience.
The Northern Ireland Public Services Ombudsman was later contacted by East Derry MLA Caoimhe Archibald on behalf of the family.
In a written response an official said the “ombudsman is precluded by the public sector employment exclusion from investigating those circumstances of the actions of the fire service”.
Seamus McCloskey said his family has been left “disappointed”.
“This is supposedly a public service ombudsman,” he said.
“How come they are unable to investigate the public service – the Northern Ireland Fire and Rescue Service.”
Sinn Féin councillor Sean McGlinchey said ombudsman Marie Anderson should meet the family.
An ombudsman spokesman said: “As Mr McCloskey was acting in the course of his employment when he lost his life, the ombudsman is precluded by the public sector employment exclusion from investigating the actions of the fire service.
“She has offered to meet with the family, through their MLA, to discuss this and other issues they may want to explore.”