More than 1.1 million patients a year who need urgent medical attention are waiting too long for ambulances, figures show.
Ambulances we re late to 35% of all life-threatening emergencies - category A calls - in the 12 months to the end of August, according to NHS England figures analysed by the Daily Mail. Ambulances should arrive on the scene for these most urgent calls within eight minutes.
Separate figures obtained by Labour under the Freedom of Information Act showed that thousands of patients taken to hospital by ambulance face long delays before being seen by A&E staff.
Ambulances should be able to hand over patients to A&E staff within 15 minutes of arrival but the figures showed the number of waits of more than an hour nearly trebled in two years.
There were 76,725 waits over an hour in 2015/16, up from 28,162 in 2013/14.
The number of waits of more than 30 minutes rose by 60% over the same period, from 258,000 to nearly 413,000.
Delays occur when there are no A&E staff available for the ambulance crews to hand patients over to.
They then have to wait with their patients - menaing ambulances are not free for other 999 calls.
Shadow health secretary Jon Ashworth said the figures illustrated the "scale of the crisis" facing the NHS.
He said: "The figures speak for themselves.
"It is clear that this Government has failed to grasp what is happening in our overstretched hospitals."
An NHS England spokeswoman said the waits were down to "increasing demand".
But she told the BBC that patients who were delayed were still receiving care from "skilled ambulance staff".
She added: "Staff work hard to keep these occurrences to a minimum."
Unison union head of health Christina McAnea said: "There's a national crisis in the ambulance service because of an extreme lack of funding across every part of the NHS.
"The relentless pressures of the job mean experienced staff are leaving, and aren't being replaced quickly enough because of the cash squeeze. Too few staff means overstretched crews and patients waiting for longer.
"As winter approaches, the demands on the already-at-breaking point NHS will increase."