A&E departments are facing a "serious problem", a health minister has said, after NHS chiefs ordered urgent action to tackle growing pressures.
Rising attendances have meant A&E units in England have started struggling to hit the four-hour waiting time target.
The problem has got so bad that NHS England has pledged extra money to help hospitals that are struggling.
But Health Minister Anna Soubry warned there would be "no quick and easy solution".
She said: "We have a serious problem, we've had a problem for a while.
"If you look at the number of people presenting to A&E it's grown by a million in just the last year.
"And unfortunately unless we take urgent action, which we've been doing, it's a problem which will grow. It's very complicated. There is no quick and easy solution."
In recent months reports have emerged of hospitals setting up temporary waiting areas in car parks and storerooms to cope with queues.
Ambulances have also been forced to wait to drop off patients.
The situation prompted the Care Quality Commission to issue a stark warning about the future of A&E.
CQC chairman David Prior said: "Emergency admissions through accident and emergency are out of control in large parts of the country. That is totally unsustainable."
He added that there was no cast-iron guarantee that there would not be a repeat of the situation at Stafford Hospital.
Mr Prior is also reported to have suggested the large-scale closure of hospital beds and investment in community services.
He added: "The patient or resident is the weakest voice in the system. It is a classic market failure. The user doesn't know nearly as much as the professionals, even with the internet."
Mr Prior is not alone in proposing a radical shake-up of A&E services.
The College of Emergency Medicine, which represents casualty department doctors, believes that between 15% and 30% of patients admitted could be treated elsewhere.
Soon after the CQC warning was made, NHS England announced it was asking regional health bosses to work together to ensure plans are in place for each A&E in their patch by the end of the month.
Extra money is being made available where problems are identified.
Prof Keith Willett, of NHS England, said: "When pressure builds across the health and social care system, the symptoms are usually found in the A&E department.
"We need the whole NHS system, in the community and hospitals, to recognise the problems and help to relieve the pressure on their colleagues in A&E."
A review, led by medical director Sir Bruce Keogh, is already under way to address the issues in the long term.