Hampshire County Council is currently plugging an £80m black hole by April 2023, with cuts to budgets across most departments.
But by the 2025/26 financial year the county council could have a 'staggering' net budget deficit of £237m, raising major concerns about the long-term economic state of the council.
Director of corporate operations, Rob Carr, said: 'The picture does look quite bleak.
'Our expectation is that funding will remain flat, but we have significant issues with growth in adult social care costs and inflationary pressures in energy and construction.
'There simply is not enough money coming from the government sustain the growth we are experiencing, and we don't have the firepower to address the funding gap ourselves.'
The £237m figure is an estimate based on current projections - but Mr Carr warned the final total could be even higher.
Cllr Steve Forster, executive member for commercial strategy, estates and property, said: 'We need that support from government - but I think what we have is a pragmatic budget to go forward that highlights the areas where we need the most help.
'We're still one of the three lowest council tax areas in the country, so that's also something we need to think about.'
The county council is already making cuts of £80m for April 2023.
Opposing Liberal Democrat leader, Cllr Keith House, said: 'Over the past few years we have had increasung difficulties.
'In the long-term, our financial position is not good because the ongoing pressures are always greater than our income.
'For example, the level of extra spending we've had to put into social care over the past few years has been phenomenal.
'This isn't a political point - we all live in the same county, dealing with the same problems. It's way more than we've ever had to face before.'
County council leader, Cllr Keith Mans, added: 'There are serious issues with local government finance.
'The government has to think carefully to ensure our services don't just get flat funding when demand is going up.
'I agree that there does need to be a reset in local government.'