Target times for ambulances to reach seriously ill patients are not being met, figures show.
For the last three months, ambulance trusts in England have failed to meet the target for reaching critically ill patients who are not breathing or do not have a pulse.
This means thousands of patients are waiting longer for help to arrive.
Rules say that immediately life-threatening calls classed as "red 1" must have an emergency response within eight minutes in 75% of cases.
The same percentage of "red 2" calls - which are still serious, such as strokes or fits, but less immediately time critical - must also be responded to within eight minutes.
The latest data from NHS England shows that 73.6% of red 1 calls were responded to in eight minutes in August, down from 74.5% in July and 74.8% in June.
There were 13,813 red 1 calls in August that resulted in an emergency response, and 10,173 were responded to within eight minutes.
Some 69.7% of red 2 calls had an emergency response in eight minutes in August, down from 70.6% in July and 71.4% in June.
There were 254,524 red 2 calls that resulted in an emergency response, of which 177,485 resulted in a response within eight minutes.
Other data from NHS England showed more than 23,000 patients over the last 12 months were treated outside a key cancer target, according to calculations from Labour.
The NHS is required to begin treating 85% of people within 62 days of a GP referral for suspected cancer.
But the latest data shows this target is not being met.
Shadow health secretary Heidi Alexander said: "It is deeply concerning that waiting time targets for cancer patients are being continually missed, it shows just how far the NHS has declined under David Cameron.
"The NHS is under pressure as a direct result of decisions this Government has made."
Dr Barbara Hakin, national director of commissioning operations for NHS England, said: "We continue to perform at a high level on emergency response times to the most critical calls.
"This comes as the number of the most urgent calls handled by our 999 teams has gone up by 6% over the last year, an increase of 186,000 to 3,140,000."