Members of London's Fire Authority have narrowly voted against plans to close 10 stations and cut 550 firefighters' jobs - but the mayor may try to overrule the decision
London Fire Brigade's (LFB) cuts are aimed at saving £28.8m over two years.
The plan was revised and two fire stations earmarked for closure were saved after a public consultation.
Members voted 9-8 against the plans but Mayor of London Boris Johnson has the final say.
Mr Boris Johnson was expected to consider a Mayoral Direction to go through with the cutbacks regardless of the vote.
A spokeswoman said he would now consider the development before deciding how to proceed.
Mr Johnson said: "I am disappointed the Fire Authority has once again shirked their responsibilities to deliver a balanced budget, leaving the service in an increasingly precarious position.
"I am seeking advice so this can be rectified as quickly as possible to provide financial and organisational stability for London's fire service."
The Fire Brigades Union (FBU) warned the cuts, which could see the loss of 14 fire engines, would "increase response times" and so put lives at risk, a claim denied by LFB.
A protest march across London Bridge earlier on Thursday was attended by a few hundred firefighters, BBC London reporter Marc Ashdown said.
London fire commissioner Ron Dobson said: "We have to acknowledge that the number of fires we attend has gone down by half in the last 10 years, and our latest figures show that fires continued to fall at the same rate last year.
"Under my revised proposals, response times in London will remain amongst the very best of any emergency service in the UK and firefighters will continue to carry out community safety work to prevent fires at the same level as they do now."
A survey of 1,500 Londoners conducted for the FBU found 70% believed the cuts would put public safety at risk.
FBU regional secretary Paul Embery said: "These cuts are dangerous and wrong. They would lead to increased response times for millions of Londoners, which in turn would cost lives.
"There has been massive public opposition to the cuts. Londoners cherish their fire service, and they don't want to see it decimated."