David Cameron will call for patients to be treated with dignity and respect as hospitals are told to end the practice of discharging vulnerable people from wards during the night.
Professor Sir Bruce Keogh, the Medical Director of the NHS, has written to Strategic Health Authorities urging them to "urgently" review their practices after it emerged hundreds of thousands of patients are sent home in the middle of the night.
His warning comes as the Prime Minister meets nurses in Downing Street to discuss efforts to improve care and "restore a sense of pride" to the profession.
Mr Cameron is to host the first meeting of the Nursing and Care Quality Forum, announced in January to address concerns about the way some patients are treated.
Sir Bruce wrote: "While some patients may of course choose to be discharged during these hours, the examples highlighted of elderly patients being left to make their way home by themselves in the middle of the night are obviously unacceptable, and need to be addressed urgently."
Sir Bruce will be meeting SHA medical directors next month to take stock of progress.
Freedom of Information requests by The Times discovered that, out of 100 NHS trusts, 239,233 patients had been sent home between 11pm and 6am last year. If all other trusts were discharging at similar rates, this would add up to 400,000 such discharges every year, almost 8,000 a week.
Sir Bruce said in his letter that the issue was central to efforts to "put quality at the heart of the NHS". "As health professionals we all agree that patients should be treated with compassion, so it is simply not acceptable to send people home from hospital late at night when they may have no family members nearby to support them," he said.
Mr Cameron will ask the panel to research ways of ensuring that nurses have the time to provide proper care. He also wants to explore methods of using patient feedback to improve services. Last year, the Care Quality Commission found a fifth of NHS hospitals were breaking the law on care for the elderly, while 40% did not offer dignified care.
"Nurses are some of the most caring, compassionate people in the country and I want to do everything possible to allow them to do a fantastic job," he said. "That means learning from the best - and helping everyone to match those great standards."