Patient care has deteriorated in the past year with many hospitals facing severe financial problems, according to a report.
In a detailed review of the 2015/16 financial year, the influential King's Fund think-tank found 67% of NHS trusts ended the year om deificit - including 86% of acute hospitals.
Some 65% of NHS trust finance directors thought patient care had got worse over the last year, as did 54% of finance heads from clinical commissioning groups, which look after a large chunk of the NHS budget and manage local services.
More than half of finance directors expect their trust to end the next financial year in deficit, too, and are "very pessimistic", the report said.
These findings "are the most worrying" since the King's Fund began asking this question in 2012, the report said.
The top three concerns of trust finance directors were:
Delayed transfers of care, so-called "bed blocking", which is at its highest level since 2008 - this occurs when people are medically fit to leave hospital but do not have the right care in place in the community for them to be able to go home
Performance against the four-hour A&E waiting times target, which is currently the worst on record
Staff morale was being affected by pressures on the NHS
Some 38% of NHS trust finance directors are also concerned about achieving their savings plans this year.
The report said extra cost pressures this year and next will "all but wipe out" the front-loaded money given by the Government as part of the Comprehensive Spending Review.
There are also worries in more than half of trusts about being able to recruit doctors and nurses to plug shifts following the introduction of a cap on agency spending by the Government.
The report also confirmed that 8% of patients - more than 1.85 million - spent longer than four hours in A&E across the year, the worst performance since 2003/4.
The number of patients waiting for hospital treatment is estimated to have risen to 3.7 million, an increase of 17% (almost 500,000 patients) over the year and the highest number since 2007.
Shadow health minister Justin Madders said the report is "another reminder that Jeremy Hunt has completely lost control of NHS finances".
Health minister David Prior said: "We recognise parts of the NHS are under pressure as demand rises in large part due to our ageing population, but we are supporting the NHS's plans to deliver more care outside hospital settings and improve performance, including by reducing the use of expensive agency staff."