Fire chiefs are offering staff £1,000 a shift to cross picket lines during expected strikes.
Crews nationwide have voted to walk out as soon as next month unless they get a revised pay offer.
Hertfordshire Fire Service responded with an offer of bumper pay for those ignoring the strike.
It wrote to staff offering £1,000 for “resilience fire cover”.
The cash will be paid for covering a single 24-hour shift even if only an hour is worked.
The offer is open to roles including firefighters, crew commanders, station commanders and fire control operators.
The Fire Brigades Union called it “an insult” and “a terrible waste of public money”.
General Secretary Matt Wrack said: “If the money can be found to pay people these kinds of sums to break strikes, it can be found for a decent pay deal.
“What is being reported about Hertfordshire is likely to be the tip of the iceberg.
“All over the country, fire and rescue services will be putting in place contingency arrangements – very often at great expense.
“This is an insult to firefighters who are struggling after more than a decade of falling pay.
“It also represents a terrible use of public money.
“We registered a pay claim in May 2022 and have been trying to negotiate a settlement ever since.
“The average firefighter has lost the real terms equivalent of about £4,000 a year in pay since 2010. We want to resolve this dispute without striking and it’s up to the employers to come forward with a decent pay offer.”
Hertfordshire Fire Service said: “We hope this dispute can be resolved and that a nationwide strike can be avoided.
“However, like all fire services, we need contingency plans to meet our statutory obligations.
“While we support firefighters’ right to strike and understand their concerns, we have a duty to keep people safe and need to ensure that if someone calls 999 with a life-threatening emergency during a strike that someone will come and help them. We have therefore been looking at ways to secure enough cover from fully qualified firefighters.
“This resilience plan has included in it an option of additional payments to firefighters who are willing to respond during strikes.”
More than 80% of Fire Brigades Union members balloted last month voted to strike.
The union says that since 2010 crews have experienced a 12% drop in real terms earnings.
It also says that in the same period about one in five jobs have been cut.
If the strike goes ahead it will be the first nationwide walkout over pay in 20 years.
