The London Fire Commissioner has proposed the closure of 12 fire stations in the capital with the loss of 520 jobs.
The plan put forward by Ron Dobson is designed to save £45m over the next two years.
Mr Dobson said around 10% of frontline firefighter posts will be axed, adding that he hoped to avoid compulsory redundancies.
The number of fire stations would be reduced to 100 under the proposals, which will go before the fire authority later this month.
The commissioner said he hoped firefighters would not take industrial action over the planned cuts, stressing that the authority had to make savings because of reductions to its budget.
However, Sky News can reveal the risk of industrial action has been heightened by the proposal.
A London firefighter said: "I can imagine we will be going straight back to our unions as we were told there would not be any cuts to the budget.
"We were under the impression this proposal would not be made."