Nearly 1,000 people waited over 12 hours to be admitted to A&E departments in England in January.
It is the highest figure on record for so-called "trolley waits", according to new figures from NHS England.
The equivalent number for January 2016 was just 158.
A total of 79,545 people were kept waiting more than four hours to be admitted, another record high.
The figures show the scale of the pressure NHS hospitals faced during January.
The proportion of patients seen within four hours of arriving at A&E was the lowest on record: 85.1%. The target is 95%.
The number of people waiting more than two months to start cancer treatment after an urgent referral hit a new high of 2,437, or roughly one in five of patients seen by GPs.
The target for this type of referral is 85%, but in January the level was just 79.7% - the lowest on record.
Meanwhile delayed transfers of care, also known as bed-blocking, were the second-highest on record.
The total number of hospital days lost through delayed transfers were 197,054 - up 23% on January 2016.
Nuffield Trust chief economist and director of research John Appleby said the figures made for "dismal reading" for the NHS and patients.
"The numbers of patients stuck on a trolley waiting for a hospital bed have gone through the roof. These are vulnerable people with acute medical needs. Corridors, it seems, have become the new emergency wards.
"The problems in social care are well known and cuts to services have been a big driver of these problems. That's why the extra money announced in yesterday's Budget is welcome.
"But with the NHS experiencing its own pressures and the social care funding gap set to be at least £2 billion in the coming year alone, there are no guarantees that patients at A&E can expect let-up any time soon."