Staff at the Food Standards Agency (FSA) are being balloted for strike action that could affect meat supplies during the festive season.
The dispute involving several hundred inspectors, vets, and office-based staff in England, Wales and Northern Ireland could bring the industry to a halt, according to the union.
Earlier in the year, FSA staff voted to reject a pay offer of between 2% and 5%.
UNISON says this is significantly lower than inflation – currently 9.9% – and falls short of the 10% pay claim put forward by the union.
The ballot closes on 31 October. UNISON says this could result in strikes in the run up to and over Christmas leading to less meat on supermarket shelves.
UNISON head of local government Mike Short said: “FSA staff play a vital role in keeping contaminated meat off people’s plates.
“But many have to work in a difficult and unpleasant conditions inspecting carcasses for signs of disease.
“These employees protect consumers, ensure good animal welfare, and must be rewarded accordingly.
“The FSA needs to come up with a significantly higher offer to avoid any disruption.”