Eleven hospital trusts are being placed in special measures because of major failings, the government has announced.
Health Secretary Jeremy Hunt said the trusts, among 14 investigated for high death rates, had problems so entrenched that tough action was needed.
He cited examples of staffing problems, poor care and weak leadership as he announced the move in Parliament.
The other three trusts investigated in England were also told to make improvements following the review.
But the health secretary said investigators had confidence the leadership at those trusts was capable of making the changes needed.
As part of the process of special measures for the other 11, teams of external experts will be sent into the organisations to work with the senior management team.
Regular updates on their progress will also be given, while unsafe practices have been stopped immediately.
For example, two operating theatres have been closed at one site because of inadequate maintenance records.
The review team said while the failings were significant they had found nothing on the scale of the Stafford Hospital scandal, which prompted this investigation.
Mr Hunt set out a detailed breakdown of the problems identified at the individual trusts, but among the common themes listed were:
• Patients being left on trolleys, unmonitored for excessive periods and then being talked down to by consultants
• Poor maintenance in operating theatres, potentially putting patients in danger
• Patients often being moved repeatedly between wards without being told why
• Staff working for 12 days in a row without a break
• Backlogs in complaints
• A patient inappropriately exposed where there were both male and female patients present
• Low levels of clinical cover - especially out of hours
• Hospital boards being unaware of potential problems, including a spate of still births
Mr Hunt said: "We have taken swift and tough action to make sure these hospitals are given all necessary support to improve.
"We owe it to the three million people who use the NHS every week to tackle and confront mediocrity and inadequate leadership head on."
'Not good enough'
The investigation into the 14 trusts was launched earlier this year following the public inquiry into the Stafford Hospital scandal, which said the public had been betrayed by a system which put "corporate self-interest" ahead of patients.
The trusts were identified as they had the highest death rates in 2010-11 and 2011-12.
The probe has been led by NHS England's medical director Prof Sir Bruce Keogh and focused on whether the figures indicated sustained failings in the quality of care and treatment at the trusts.
Sir Bruce said: "Not one of these trusts has been given a clean bill of health by my review teams.
"These reviews have been highly rigorous and uncovered previously undisclosed problems.
"I felt it was crucial to provide a clear diagnosis, to write the prescription, and, most importantly, to identify what help these organisations might need to support their recovery or accelerate improvement.
"Mediocrity is simply not good enough and, based on the findings from this review I have set out an achievable ambition which will help these hospitals improve dramatically over the next two years."
The 11 trusts in special measures are: North Cumbria University Hospitals NHS Trust, Northern Lincolnshire and Goole Hospitals NHS Foundation Trust, Tameside Hospital NHS Foundation Trust, United Lincolnshire Hospitals NHS Trust, Basildon and Thurrock University Hospitals NHS Foundation Trust, Burton Hospitals NHS Foundation Trust, East Lancashire Hospitals NHS Trust, George Eliot Hospital NHS Trust, Sherwood Forest Hospitals NHS Foundation Trust, Buckinghamshire Healthcare NHS Trust, Medway NHS Foundation Trust.
The other three investigated are: Blackpool Teaching Hospitals NHS Foundation Trust, The Dudley Group NHS Foundation Trust and Colchester Hospital University NHS Foundation Trust.
Between them the trusts run 19 acute hospitals (16 among those trusts on special measures). There are 160 acute trusts in England overall.
Mr Hunt sought to blame the last Labour Government for failing to expose flaws in the NHS.
But Shadow Health Secretary Andy Burnham dismissed the charge, and accused Mr Hunt of "playing politics with people's lives".
Peter Walsh, chief executive of Action Against Medical Accidents, said the findings were "scandalous".
"The hospitals concerned should have been investigated years ago."