Jobs will be axed, wards closed and front-line services radically redesigned under a national drive to cut 20bn from NHS budgets.
Hospitals are bearing the brunt of cutbacks as more patients are treated more cheaply in the community and at home.
But the measures last night prompted warnings of sweeping cuts to front-line care and a return to the long waits for treatment of the 1980s.
Analysis of three-year plans of the region's highest-performing foundation hospitals show all must make deep cuts to balance the books.
The hardest hit is Barnsley's hospital where savings targets are almost double other centres as bosses predict revenue will fall by nine per cent by 2012-13 from a high last year.
Hospitals in North Yorkshire warn they face significant uncertainties because of continued instability in NHS finances in the county. Managers at York's hospital plan savings of 32m over three years, with cuts of 13m in Harrogate.
Adult hospitals in Sheffield require efficiencies of 100m in the three years to 2013 on annual budgets of 800m, while Sheffield Children's Hospital aims to cut costs by five per cent every year for three years. Its position has been thrown into further doubt over Government plans to cut payments to children's hospitals.
A total of 51.5m will be saved in Doncaster in the next three years and 50m in Bradford. Hospital chiefs in Rotherham estimate they need cost cuts of up to 20 per cent.
Ministers claim they have protected NHS budgets.
But hospitals will lose income as services are moved into the community and are already facing cuts in payments for remaining services amid signs many are already struggling to hit efficiency targets.
John Cafferty, head of health at Unison in Yorkshire, said: "I don't think it's scaremongering to say that we risk heading back to a return of the NHS of the 80s and 90s, when people waited for hours, if not days, on trolleys.
"The Tory-Liberal Democrat coalition is being at best deceitful and at worst telling direct lies regarding the supposed protection to NHS budgets. The full scale of the cuts required cannot be absorbed by efficiency savings."
Barnsley East Labour MP Michael Dugher said he was worried about the local impact of cuts as Ministers order a massive revamp of how the NHS is run.
"Why is the Government wasting billions on an expensive and unnecessary re-organisation of the NHS rather than putting the money into front-line care where it is needed?" he asked.
The King's Fund thinktank said the NHS faced the "biggest financial challenge in its history".
Sue Slipman, of the Foundation Trust Network, said: "Everyone recognises it will be enormously tough to achieve and a lot of it will be dependent on how workforces are flexible at a local level.
A Barnsley hospital spokesman claimed the scale of efficiencies was commensurate with other trusts. It had "no alternative" to reduce jobs but no redundancies had so far been needed.
"We are also determined to ensure that we deliver our services in line with what our community tells us it wants, which often means at home or close to home, and not always in the hospital."