NHS services in Calderdale and Huddersfield face a budget shortfall of more than £280m over the next seven years.
But health bosses could secure £490m in funding if a planned shake-up of NHS services goes ahead.
Calderdale and Huddersfield NHS Foundation Trust (CHFT) is “financially unsustainable” and has a funding gap of £204m by 2021-22.
A report by Calderdale and Greater Huddersfield Clinical Commissioning Groups (CCGs) said: “Overall, despite exceeding national expectation on efficiency savings, CHFT is no longer financially viable as it is currently configured.”
In the same period the CCGs’ combined funding gap is £59.7m. Their combined budget will increase by 8.69 per cent - way short of the expected increase in expenditure of 15.6 per cent.
There is a further shortfall of £17.2m for other NHS providers, bringing the combined total to £281m.
Financial pressures included the cost of running two A&E departments less than six miles apart, the report said.
The hospital trust is also making costly repayments for Calderdale Royal Hospital, which is leased back from the private sector under a Private Finance Initiative (PFI) scheme.
Bosses considered building a new hospital and vacating the existing sites, but are unable to do so because of a £200m “break clause” in the PFI contract. The CCG report said there was “no negotiable exit route” from the PFI.
The report said Calderdale being the main emergency site was the most affordable option.
It said: “The preferred option is dependent upon securing external funding support of £490.4m.”
Read more about the A&E proposals at Calderdale Royal Hospital and Huddersfield Royal Infirmary: