Around 8,500 "bed-blocking" patients are stuck in NHS hospitals every day - costing the health service £900 million a year and driving up use of the private sector, a report shows.
The review into how the NHS can save cash found bed-blocking - which occurs when patients are medically fit to leave but care has not yet been organised in the community - is a bigger problem for NHS hospitals than previously thought.
In the wide-ranging report, commissioned by the Government, Lord Carter of Coles sets out the way NHS hospitals can cut costs in a bid to save £5 billion a year by 2020.
The study suggests cuts to the numbers of staff working in NHS pharmacy and administration, the sharing of purchasing power between NHS trusts to get the best prices on goods and services, and cuts to the variation in how patients are treated to improve care and save money.
The report also points to large differences between trusts in staff absence and sickness rates and the need for a better grasp on what staff are doing.
It said some NHS trusts have moved to a "call centre" model for handling some patient calls and appointments, while others have "patient portals that allow the patient to directly manage their own bookings which enables administrative cost reductions".
On bed-blocking, it said the number of days lost is higher than previously thought, which is forcing the NHS to turn to the private sector to take on planned operations such as knee and hip replacements.
It said: "Nearly all trusts wrestle with the problem of moving those who are medically fit into settings that are more appropriate for the delivery of their care or rehabilitation, and for the families and carers.
"Official statistics on delayed transfers of care show a recent increase to around 5,500 patients per day.
"However, information provided by trusts reveals that the problem could be much larger and we estimate that on any given day as many as 8,500 beds in acute trusts are blocked with patients who are medically fit to be transferred.
"The cost of these delays to NHS providers could be around £900 million per year.
"These delays also have a knock-on effect resulting in cancellations of elective operations because of a lack of bed capacity, and work going out to the independent sector.
"NHS expenditure in the non-NHS sector has increased in recent years, and currently stands at over £11 billion per annum."
The report said the number of knee procedures being carried out by private hospitals on behalf of the NHS has risen by 60% since 2011.
Official NHS figures show that from January to November 2015, 1.59 million days were lost in total to bed-blocking - a figure that is already bigger than for any previous year.
In the whole of 2014, 1.56 million days were lost, while 1.4 million were lost in 2013 and 1.37 million in 2012.
Lord Carter's review also calls for a reduction in the differences between hospitals in the quality and cost of care.
It said the average cost of an inpatient treatment is £3,500 but there is 20% variation between the most expensive trusts (£3,850) and the least expensive (£3,150).
The report found the average bill for new hip joints varied from £788 to £1,590.
Sickness and absence rates among staff also varied, from 2.7% to 5.8%.
It said improving staff productivity by five minutes every shift could save the NHS £280 million a year.
And with better procurement, the NHS could save £700 million every year.
The report added: "A sample of 22 trusts use 30,000 suppliers, 20,000 different product brands, over 400,000 manufacturer products codes and more than 7,000 people are able to place orders."
Lord Carter said: "My experience of the NHS and hospitals internationally is that high-quality patient care and sound financial management go hand in hand.
"To improve the quality of care, hospitals must grasp resources more effectively, especially staff, which account for more than 60p of every pound hospitals spend."
Health Secretary Jeremy Hunt said: "I want to make the NHS the safest healthcare system in the world, capable of providing the same world-class care every day of the week, powered by a culture of transparency and learning.
"This ground-breaking review will help hospitals care for patients, making sure every penny possible is spent on front line patient care and bureaucracy is slashed so doctors and nurses can concentrate on caring."
Shadow health secretary Heidi Alexander said: "This report is absolutely right to highlight the huge financial pressures that delayed discharges are placing on the NHS.
"However, ministers cannot shy away from the fact that this is a crisis in care that has happened on their watch."
The report comes as a separate study from the National Audit Office (NAO) found that in 2014 there was an overall staffing shortfall of around 5.9% in the NHS, equating to a gap of around 50,000 clinical staff.