Nearly 3,000 patients a day had to be cared for in hospital corridors or make-shift treatment areas rather in a bed on a ward in England last month, figures show.
It is the first time the data has been published and reveals the scale of the challenge facing the NHS in tackling what ministers say is "unsafe" and "unacceptable".
It is defined as when patients spend more than 45 minutes being treated in make-shift areas, including corridors, side-rooms and even car parks or when they are left on or near wards with no bed.
The daily number represents 3-4% of patients coming into hospital via A&E every day.
The figures show during May there were 2,241 patients a day, on average, who experience corridor care while in A&E, with another 669 experiencing it on or near to wards inside the hospital.
NHS analysis found that 20 trusts accounted for more than half of the cases of corridor care in A&E, while 20 trusts also accounted for more than two thirds elsewhere in hospitals.
Staff and patients have told BBC Your Voice of the problems they have experienced with corridor care.
Suzanne has taken her mother, in her 80s, to A&E in the East Midlands five times this year. Every visit meant more than 24 hours waiting in a corridor.
"Mum was one trolley in a sea of trolleys," Suzanne recalls.
Confused and distressed, her mother was only helped to the toilet or given a drink because family were there, she says.
"If we hadn't been, I dread to think what might have happened."
Kathy's experience was no better. Sent in by her GP one morning earlier this year with a suspected eye infection, she waited 36 hours in a chair, alone, in a hospital in the East of England before being told her blurred vision was caused by a brain tumour.
"It was horrendous… I got home and threw up. I was exhausted and broken."
Nurses, who asked to remain anonymous, described burnout and impossible conditions.
One recalled a shift where the corridor was lined with patients. A body had to be wheeled past them on its way to the mortuary. Later, another patient went into cardiac arrest in the same corridor.
"Those frail patients watched chest compressions. There's no dignity in that."
Another nurse said her emergency department felt "like a war zone". She described a patient who died unnoticed in the corridor.
"He'd started to stiffen because he had been there for so long, dead, with no-one noticing. It's horrific to think someone's loved one died with no one near them."
Ministers have pledged to eradicate the practice by 2029.
Health Secretary James Murray said: "Corridor care is unacceptable, undignified and has no place in our NHS.
"That is why, for the first time, we are publishing this data to shine a spotlight on where the problems are greatest and ensure trusts get the support they need, with the vast majority of corridor care concentrated in a small number of organisations."
Siva Anandaciva, of The King's Fund health think tank, said: "These figures confirm the scale of something that should never have been normalised in the NHS.
"The sheer scale of corridor care in the NHS is deeply concerning."
He said it was a "positive step" to have the figures in the public domain, but added:
"We have had data on long waits in other parts of the NHS for decades – including A&E departments - and it has done little to stop their rise."
Additional reporting by Kris Bramwell.
