Lives are being put at risk because ambulances are taking up to three minutes longer on average to reach the most seriously ill patients, according to Labour.
Chaos at accident and emergency departments means ambulances are trapped in queues outside, which has a knock-on effect on the time it takes to deal with 999 calls, the party said.
Records published by the Health and Social Care Information Centre show life-threatening call outs are taking an average of 67 seconds longer than in 2011.
That rises to two minutes and 21 seconds in the East Midlands, taking its response time just over the target eight minutes.
Shadow health secretary Andy Burnham said: "These figures raise real concerns that lives are being put at risk by the chaos in the NHS."