Health Secretary Jeremy Hunt has acknowledged that failure to hit A&E targets was "not acceptable" but insisted that the Tories were increasing funding and recruiting more doctors and nurses.
Labour said the failure to meet the four-hour A&E target in England was "symptomatic of the crisis that the Tories have left our NHS in".
But Mr Hunt insisted that health outcomes had improved in the last five years and focusing on the targets was not a "fair reflection" of NHS performance.
On the A&E target, Mr Hunt said: "The standard says that you should be seen within four hours, not just seen but also treated and either discharged home or admitted to hospital."
On BBC One's Andrew Marr Show he admitted: "We haven't hit it for over two years, it's not acceptable. We have a plan to get back to that standard."
He added: "You have got to look at what actually happens in A&E departments, which is despite the huge pressure of an ageing population - half-a-million more over-75s since 2010 - we are actually seeing, within that crucial four-hour standard more than 2,000 people every single day.
"Demand has gone up faster than that, which is why we are investing in more doctors, more nurses, putting in more funding than ever before."
A separate target is for 92% of patients to be treated within 18 weeks of referral by their GP.
But the NHS has not hit this target since February 2016 and performance has been slipping since then.
Mr Hunt said: "They are very important standards, but they are not the only standards."
Insisting that focusing on the targets was not a "fair reflection of the performance of the NHS" he said: "Just before the election was called, at the end of March, the NHS published an independent report in which they said that if you take most major conditions - heart attack, stroke, cancer, so on - outcomes have dramatically improved over the last five years."
Responding to Royal College of Nursing claims that nurses are seeking debt advice and increasingly turning to food banks, Mr Hunt said: "The minimum a nurse can be paid in this country is £22,000 - £27,000 in inner London."
The average pay was £31,000, he said.
"Is that enough considering the brilliant work that they do? I think many people would say they want to pay them more. I think they do an incredible job.
"If you want more money to go into the NHS - and this Government recognises we will need to put more money into the NHS and the social care system because of the pressures we face - then the question is how you get there."
Shadow health secretary Jonathan Ashworth said: "We've now had an admission of failure straight from the horse's mouth: the Tory-made A&E crisis is simply 'not acceptable'.
"Jeremy Hunt this morning was forced to admit to the British public that the four-hour A&E target has not been hit in over two years. This shameful statistic is symptomatic of the crisis that the Tories have left our NHS in. Britain cannot afford another five years of Tory failure.
"Only Labour will give the NHS the resources it needs to deliver the service patients deserve."