Merseyside fire crews start an overtime ban on January 12 in a dispute over cuts to frontline fire services.
The Fire Brigades Union says the cuts involve the loss of up to 104 frontline firefighter posts including 36 frontline posts being moved to non-operational work.
The FBU says the ban will expose the "chronic shortage" of firefighters in Merseyside.
Pre-arranged overtime is completely voluntary in Merseyside fire service and cannot be used to cover firefighter shortages.
The fire authority has also extended the use of the controversial staffing system to Eccleston fire station which means longer response times, extended working hours and the loss of firefighter posts.
The Fire Brigades Union says this breaks an agreement to seek the involvement of ACAS.
Les Skarratts, Merseyside FBU brigade secretary said: "There have been relentless cuts to fire services in Merseyside and there is now a chronic shortage of crews at fire stations. These cuts have already had a real impact on the number of frontline firefighters to crew fire engines and attend 999 emergencies.
"This new set of planned cuts will mean even fewer firefighters spread more thinly taking longer to get to incidents.
"These are real cuts to the number of frontline firefighters in Merseyside which will impact on how we respond to 999 emergencies.
"Merseyside fire service appears to relish these cuts while promising more and more to come. An overtime ban will show how bad the chronic shortage of fire crews is and why more cuts will make that worse.
"We are taking the action needed to resolve the dispute in order to protect members delivering frontline fire services from this further round of cuts in Merseyside.
"The fire authority needs to think again about where years of cuts have brought us to and what will be left of our emergency responses if they continue."
Merseyside FBU members voted 3-to-1 in favour of action short of a strike in a ballot result announced on December 22. THE GLOBE