The next government will inherit a health service that has run out of money and waiting times for patients are likely to get worse, according to a leading think-tank's review of the NHS under the coalition.
The report by the King's Fund said that as the election approaches all areas of the NHS are feeling the strain, highlighting particular concerns about the missing of key waiting-time targets for A&E, hospital treatment and cancer treatment, increased hospital bed occupancy and delayed discharges of patients and low morale among staff.
Although it pointed out that the number of hospital-acquired infections such as MRSA and Clostridium difficile (C. diff) have substantially fallen over the past five years, "dangerously high" levels of bed occupancy - meaning staff sometimes do not have time to properly clean them between patients - could lead to a rise.
King's Fund's chief economist John Appleby told a briefing that bed occupancy is currently slightly under 90% on average but some hospitals are reporting 100% occupancy.
The number of beds has reduced by about 2% a year, which he said was partly down to advances in medicine and so "not necessarily a bad thing", but he added there is clearly a need to use them more wisely.
The review said the increase in the numbers of doctors and nurses was positive, but nurses are expected to do much more than five years ago as it calculated an almost 10% rise in productivity. Meanwhile, the activity rates of consultants has gone down.
The charity said hospitals and other providers of care have overspent their budgets by more than £800 million and the NHS is likely to record a "substantial deficit" for the first time since 2005/6.
Mr Appleby said: "Our assessment is it's going to be very difficult indeed next year.
"My speculation would be that once the system is under pressure financially next year as well, we're going to see some real problems with waiting times and that's going to have to be addressed, and patients will really feel that.
"It's likely that the system will go into next year with an overspend - that's got to be paid by somebody.
"The Treasury could pick up the tab but it's likely the NHS is going have to find the money in future years though."
The report said while the NHS has made some progress in improving efficiency, additional funding of £8 billion a year by 2020 is the absolute minimum it requires to continue to meet patient needs and maintain standards of care.
King's Fund's chief executive Chris Ham said although the reforms brought in by the coalition "wasted" its first three years in power, it was clear there has been an increased understanding of how quality of care can be compromised by not having enough staff in the latter half of its tenure, in the light of hospital scandals seen at Mid Staffs and Morecambe Bay.
"You could say the Government deserves credit for giving priority to the quality of patient care by making sure there are enough nurses on the wards to deliver high-quality standards of patient care, even if that means blowing tight financial control," he said.
Mr Appleby said other key findings of the report, which he led, were that public satisfaction with the NHS is at its second-highest level ever.
He concluded: "The next government will inherit a health service that has run out of money and is operating at the very edge of its limits.
"While the NHS has performed well in the face of huge challenges, there is now a real risk that patient care will deteriorate as service and financial pressures become overwhelming.
"More optimistically, with the economy recovering, there could soon be an opportunity to think about public spending choices and the kind of health services we want in a fresh light.
"Future debate about the NHS should focus not on how parsimonious we need to be but on how generous we want to be."
Dr Peter Carter, chief executive and general secretary of the Royal College of Nursing, said: "There is much in this report that the political parties should be looking at urgently, including concerns over staff morale, delayed discharge and future funding.
"While the report shows increases in staff numbers, we are still playing catch-up after years of cuts and increasing demand, and staff are bearing the brunt.
"Morale is low and more and more staff are being made sick with stress because of the intolerable pressure they are under.
"Demand and financial pressure on the NHS will both increase dramatically in the coming years.
"Only a fundamental change in the way the NHS works, with better integration and co-ordination, will provide a sustainable health service for future generations.
"The next government will be judged on their ability to deliver these changes."
British Medical Association council chair Dr Mark Porter said: "This report highlights the damage done to the NHS by the Health and Social Care 2012, which distracted attention from rising pressure on services and cost billions to introduce.
"Staff have done as much as they can to protect and improve patient care but, as this report lays bare, after years of underfunding the cracks are beginning to show.
"The NHS is the best healthcare system in the world and the most efficient - there is no fat left to cut without patient care being hit.
"With an election weeks away, politicians of all parties must stop using the NHS as a political football.
"Rather than short-term political game-playing, the NHS needs a long-term, fully-funded plan to protect patient care, support frontline staff and ensure it can rise to the enormous challenges facing it."
Shadow health secretary Andy Burnham said: " Thursday 7th May is shaping up to be David Cameron's day of reckoning on the NHS.
"In 2010, Cameron said he would cut the deficit, not the NHS. What this report reveals is that he is on course to create a large deficit in the NHS.
"It is scandalous that he spent £3 billion on a reorganisation that has left the NHS worse off.
"What is clear is that the fragile NHS we now have can't take five more years like the five it has just had. It can't afford the Tories' plan for deeper care cuts in the next parliament.
"It urgently needs new leadership and a change of course. Labour has set out a better plan to restore the NHS, rebuild it as a national health and care service and invest £2.5 billion extra a year - on top of Tory spending plans - to fund 20,000 more nurses and 8,000 more GPs."
A Department of Health spokesman said: "We welcome this report's acknowledgement that we have increased the NHS budget in real terms, recruited many more clinical staff and are treating more patients than ever, just as public satisfaction with the NHS improves.
"As the King's Fund says, the NHS has 'performed well in the face of huge challenges', but if we are to continue to invest in the NHS going forward it needs to be backed by a strong economy."