A&E waiting times across the UK are getting worse as the pressure on hospitals intensifies, a report suggests.
Figures collected by the Royal College of Emergency Medicine (RCEM) over the last seven weeks showed 88% of A&E patients were treated or admitted within four hours - below the target of 95%.
The A&E target is widely regarded as a key measure of how the NHS is performing.
The report found that hospitals are also experiencing major problems discharging patients who are medically fit to go home.
In some places, around a fifth of hospital beds are occupied by patients who cannot leave - so-called "bed blockers" - because there is not the right support in the community for them.
Experts say the increasing problems in social care are having a major impact on the NHS.
The new figures are based on evidence submitted by more than 40 trusts - one in five of the total in the UK.
The RCEM's president, Dr Cliff Mann, predicted the "worst is yet to come".
He said: "The majority of hospitals have endeavoured to increase the number of beds available to cope.
"Despite this, elective operations have had to be cancelled and postponed as bed capacity is insufficient to cope."
The data shows performance getting worse since hospitals began submitting the data at the start of October.
Then, just over 92% of patients were seen in four hours, falling to 88% in the middle of November.
More than 6,300 planned operations have been cancelled over the seven-week period.
As an overall average, each site cancelled 21 operations per week, ranging from no cancellations to 137 in a single week.
The Department of Health and NHS England used to publish weekly data for England on how A&E departments were performing but have now stopped doing so.
Instead, data is published monthly but only covers figures from more than a month ago.
The most recent data published was for September, meaning there is no official published data on how England's NHS is currently performing on A&E.
In its report, the RCEM said: "The college was approached by a number of trusts/boards following the winter of 2014/15.
"Each highlighted that the greatest challenge to the four-hour standard had been issues of bed availability exacerbated by increased delays in transfers of care.
"These delays in provision of community and social care rose significantly over the winter months.
"The college also felt that regular comment regarding A&E performance failed to take account of this issue, focusing instead on attendances and admissions."
Dr Mann said health managers were aware of the problems in A&E and how to deal with them, but questioned whether the necessary action was being taken.
"A key cause is the inability of our system currently to get people out of hospital when they neither need nor want to be there and we really need to target this," he told BBC Radio 4's Today programme.
"We do know many ways in which we could be doing this, and I'm not sure that we are actually therefore taking the necessary steps in a timely fashion."
He added: "Part of the purpose of publishing this report is to galvanise people's thinking at a relatively early stage in the winter so that we can actually take action now before we get to the traditionally really challenging parts of January and February."
An NHS England spokeswoman said: "It's important patients who are well enough to leave hospital can do so at the earliest opportunity and are helped to recover with dignity and compassion.
"These figures underline both the importance of joined-up care within the NHS, and hospitals' clear dependence on well-functioning social care services - particularly for older people living at home."