Leaders of the Fire Brigades Union are to announce they intend to withdraw from a 24-year-old agreement introduced after the first, and last, national fire strike.
The decision leaves Tony Blair facing what could quickly blow up into a big public sector dispute and underlines the deterioration in relations between the government and trade unions.
Firefighters claim a formula automatically triggering annual rises for 50,000 crew members, adopted after a bitter 1977-78 walkout when army green goddesses answered emergency calls for nine weeks, has seen staff slip behind in the pay stakes.
The formula effectively prevented action over pay but representatives of every UK brigade are expected at a meeting in London today to threaten walkouts to achieve a new deal.
The FBU is seeking a one-off 10%-plus award this November for firefighters who, with four years experience, earn £412 a week. They also want the current formula, linking rises to those of male industrial workers, replaced by a new system.
Andy Gilchrist, general secretary of the FBU, said: "For the past 25 years, firefighters and emergency fire control staff have relied on a pay formula which was born out of the only national strike ever in the British fire service.
"This formula is now outdated and our members are demanding a substantial increase in pay now, and a new formula, which reflects the modern fire service, for the future."
The move is a gamble by the FBU leadership and represents a significant u-turn by a union which for nearly 20 years basked in the security of a deal that was the envy of many other groups of workers.
Guaranteeing yearly increases matching those of the top 25% of industrial workers, the FBU leader who signed the agreement - Terry Parry - even named a greyhound Upper Quartile after the formula.
The union was so anxious to protect the system during the Tory era that when John Major imposed a 1.5% pay norm across the public sector, the FBU insisted on accepting only 1.4% - eschewing the larger rise to stick to the figure produced by the deal.
But the incident also underlined how a sharp decline in the number and bargaining power of manual employees combined with low inflation had reduced the value of increases under the system.
The qualified firefighter on £412 a week or £21,531 a year after four years must wait, unless promoted, until they have put in 15 years to receive an increment that will put them on £431 a week.
FBU leaders want a formula linking wages to those of skilled and professional groups and point to official figures which show that nurses earn an average £435 a week, midwives £485, engineering technicians £497 and lorry drivers £575.
Firefighters proved in a series of recent local disputes, most notably in Berkshire and on Merseyside, that they are well organised and prepared to strike.
Local authorities acknowledge firefighters have slipped behind but are strapped for cash and say discussions would be controlled by the Department for Transport, Local Government and the Regions.
· Special report on trade unions at guardian.co.uk/unions
