Donegal County Council has granted planning permission for a new petrol station adjacent to the site of the Creeslough tragedy in which ten people were killed.
Several families bereaved by the 2022 explosion had objected to the application saying it would be "profoundly insulting and disrespectful."
However, a letter issued and signed by a senior executive planner on behalf of the council granting permission has been sent to some bereaved family members.
At least two of the families bereaved by the tragedy have indicated they are likely to appeal the decision to An Coimisiún Pleanála.
"We will speak to our legal team but we will most likely appeal this decision again," said a bereaved family member.
A decision on the new application for a service station by Donegal County Council was not due until 1 April.
There are 17 conditions attached to the permission granted to Annette and Danny Martin Lafferty.
The decision also includes wildlife protections, requiring a summer bat survey before demolition or site clearance if works have not started by then, while all demolition and site clearance must take place outside the bird breeding season from March to August inclusive.
The former store owners had previously sought to rebuild on the site of the explosion, but An Bord Pleanála determined that the proposed plan was "out of character" with its surroundings in the village.
A second application to demolish a house beside the site and build a new complex received several submissions objecting to the development.
A joint letter from the families of victims Leona Harper, 14, and mum of four, Martina Martin, said the site of the Creeslough explosion deserves the same respect as the sites of the Stardust Nightclub fire and the Grenfell Tower fire, which were never rebuilt in this way.
"It would be profoundly insulting and disrespectful to the memory of those ten individuals, and to their surviving families, to permit the construction of a similar commercial fuel facility on or immediately adjacent to the site where they died," said the families, who are represented by solicitor Damien Tansey.
The families argued that it was premature to allow a similar fuel-related development while investigations into the explosion are ongoing.
They also raised strong objections to the "complete absence" of any prior consultation with the families, saying they were neither approached nor informed before the application was submitted.
"Given that the proposed development relates directly to the site where their loved ones perished, the very minimum that basic decency and respect required, was that the families be engaged with before any such application was made."
The letter was issued on behalf of Leona Harper's parents, Hugh and Donna, her brothers Anthony and Jamie, Anthony’s partner Leah Clarke, and Martina Martin’s sisters Amanda Faul, Marie Ronaghan and Kathryn McDevitt.
Those who died in the Creeslough tragedy were Robert Garwe and his five-year-old daughter Shauna Flanagan-Garwe; Catherine O’Donnell and her 13-year-old son James Monaghan; Jessica Gallagher; Martin McGill; James O’Flaherty; shop worker Martina Martin; Hugh Kelly; and 14-year-old Leona Harper.