Dr Nick Scriven, of the Society of Acute Medicine, said: “This has been and continues to be an extremely challenging time for urgent care in the NHS, which has been overlooked amid the chaos of Brexit and the smokescreen it has created.”
He also warned that the situation could get worse even though winter has ended.
“My major imminent concern is that hospitals are working flat out at the moment and we have a looming spell of bank holidays, when many support services will not be functioning, heaping up the already relentless pressure.”
The warning comes as the NHS is paving the way to scrap the four-hour A&E target in England.
Bosses believe the four-hour target is outdated and distorts priorities because it does not differentiate between those with minor and major conditions, but emergency doctors have called for the target to be kept.
Meanwhile, there are more than four million people on the waiting list for hospital operations, such as knee and hip replacements.
That is nearly double the figure a decade ago.
But Pauline Philip, of NHS England, said hospitals were seeing rising demand, praising staff for working “tirelessly” to care for patients.