The Fire Brigades' Union plans to recall its national conference in Manchester on September 12 to discuss industrial action, after the failure of talks in central London.
"The executive council are recommending national strike action in defence of pay," the union's general secretary, Andy Gilchrist, told firefighters gathered outside the venue for the negotiations. He added that industrial action now looked inevitable.
He received loud applause from the thousands of firefighters who had taken to the streets to lobby the pay talks.
Employers had tabled an offer of a 4% pay rise but the union was demanding an increase of almost 40%.
The employers said they were "extremely disappointed" that no agreement had been made.over the firefighters' "unrealistic" demands.
The union had hoped to see the pay of a qualified firefighter rise from £21,500 a year to £30,000.
The FBU says the current pay formula, which was drafted after the last national strike in 1977, is outdated and has left firefighters underpaid.
Firemen and women from around the country gathered outside Central Hall, Westminster, where the talks were taking place. Many wore their protective coats and carried FBU flags, hooters and whistles.
Syd Hall, 51, a fireman from Oxford, said: "I'm here to support our claim for a decent living wage. The old pay offer has served its purpose. It's outdated and we've been falling behind other workers for years.
"I was in the strike in 1977 and if I have to do it again then I will. We were out for nine weeks back then and I'll go through it again if I have to."
The firefighters were joined by the leaders of other trade unions, including the general secretary of the train drivers' union ASLEF, Mick Rix, and the general secretary of the Communication Workers Union, Billy Hayes.
