Sir Albert Bore said whole services would have to be discontinued
A further 6,000 jobs will be cut at Birmingham City Council in the next four years, the authority's leader has said, making the workforce about a third of the size it was in 2010.
Sir Albert Bore said forecasts suggested there would be just 7,000 full-time staff by 2018.
He said the cuts equated to double the number of workers who lost jobs at the Longbridge car plant in 2005.
He blamed an "unfair distribution" of national government cuts.
"Colleagues, there is a ticking time bomb under this city council," he said.
"Over many years we have not given enough attention to how we manage staff reductions and plan the workforce we will need in the future.
"If we don't act now then the consequences will be catastrophic for the future functioning of this organisation."
Analysis: Kath Stanczyszyn, Political Reporter, BBC WM
Sir Albert Bore claims this projection of further drastic job cuts proves the reality of his now famous "jaws of doom" statement - despite some critics describing him as crying wolf.
And despite the likely ring-fencing of certain services, such as children's safeguarding, Sir Albert was keen to stress that it won't be quite as simple as keeping the core and getting rid of the fluff.
The leader says in order for Birmingham to remain a city where people want to live there will have to be very sensitive choices made over which services stay and which disappear.
Sir Albert said whole services would have to be discontinued but said a decision on which services would go had not yet been made.
"Clearly we cannot continue with anything like the range of activities we have delivered in the past," he said.
The Labour-led council has so far saved £460m of its £822m target by 2018. The leader said there were currently 13,000 workers at the council - not including school staff - compared with 20,000 in 2010-11. He said the figure was likely to drop to 7,000 by 2018.
He admitted it was likely most of the cuts would have to be made through compulsorily redundancies.
Sir Albert said the government had distributed the national grant cuts "unfairly between different parts of the country, with the most deprived areas receiving the biggest cuts."
He said there was a £147-per-home cut in Birmingham compared with a national average of £45
The leader said the council had launched an action plan to support workers and help them gain new skills and redeployment elsewhere.
"The years ahead will be some of the toughest this city council has ever experienced but by working together as a council and a city we will get through it," he said.
He denied the authority had been overstaffed previously.
He said there would be asset disposals but stressed there were no plans to sell off Birmingham Airport shares or the city's museum and art gallery.
A government spokesman said: "Local government accounts for a quarter of all public spending and since 2010 government has delivered a fair settlement to every part of the country, including Birmingham.
"The majority of local authorities have continued to balance their budgets whilst reducing council tax in real terms and increased or maintained public satisfaction with services.
"All councils should be making sensible savings and keeping council tax down by merging back office services or doing more joint working."
The spokesman said the government had not announced "any spending allocations for councils beyond 2015-16".
Unite regional organiser Gerard Coyne said the union was "bitterly disappointed" the authority was having to make the cuts.
"They're going to have a drastic impact on services provided by the council," he said.
Unison regional secretary Ravi Subramanian said the losses would be devastating to workers, impact on services to vulnerable people and take millions from the local economy.