The councils hardest hit by funding cuts have been revealed.
BBC research for Panorama has identified 11 authorities the Chartered Institute of Public Finance and Accountancy (Cipfa) said would have "fully exhausted" reserves within four years unless they topped them up.
The investigation was part of the network’s Panorama programme - due to air on Wednesday.
The worst hit council - Northamptonshire saw its unallocated reserves, meaning the money it has in the bank, fell by 91%.
The list in full is Northamptonshire -91%, Somerset -73%, Rotherham -62%, Thurrock -58%, Croydon -55%, Stoke-on-Trent -55%, Sutton -46%, Isles of Scilly -46%, followed by Knowsley, Greenwich and Medway all -44%.
The Local Government Association said councils faced "systemic underfunding".
The government said councils were responsible for managing their funds.
Councils have faced cuts to their government funding and rising demand for services such as social care, while MPs have warned children's services are at "breaking point".
Cash reserves - money held back for specific projects or emergencies, such as flooding - are seen as a measure of financial security.
Between them the 152 major councils in England had £14bn in reserve in March 2018, £500m more than the year before but £400m less than in 2015.
The BBC analysis of government data follows work by Cipfa, which published a "resilience" index of councils, but stopped short of naming those it warned were depleting reserves the fastest.
The warning was based on the latest data available, comparing reserves as of March 2018 with March 2015.
The analysis reveals which 11 of the 152 major English councils have used so much of their reserves since 2015 that Cipfa said they would run out within four years if spending patterns continued.
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A Ministry of Housing, Communities and Local Government spokeswoman said: "We are investing in Britain's future, and this year's local government finance settlement includes extra funding for local services.
"Local authorities will have access to £46.4 billion this year, a real terms increase that will strengthen services, support local communities and help councils meet the needs of their residents. The Government will be looking at funding for services as part of the Spending Review."