Hospital trusts have failed by a whisker to meet the government's target to treat all accident and emergency patients within four hours.
Figures from the Department of Health showed 97.9 per cent of patients waited four hours or less from arrival to admission, transfer or discharge, slightly below the target of 98 per cent. For major A&Es, the figure was lower, at 97 per cent.
In his annual report, NHS chief executive David Nicholson warned the health service it must meet its own standards or face losing taxpayers' confidence.
Mr Nicholson praised the "strong progress" of the NHS against key pledges, but singled out A&E waits. "We simply cannot allow ourselves to slip beneath this minimum standard," he said.
He added: "Minimum standards in the NHS are non-negotiable, and taxpayers' confidence in our ability to deliver will always suffer when we fail to meet them."
Elsewhere in the report, Mr Nicholson was upbeat, highlighting that the service is on track to meet an ambitious target to halve the rate of MRSA bloodstream infections.
Hospital deep cleans, matron recruitment and 18-week wait targets were also on course, he said, adding that the service was well placed to deliver on health minister Lord Darzi's next stage review.
But the NHS chief executive said the service should heed patients' concerns over issues such as mixed-sex wards.
In a further assertion of his "devolution" push, he urged managers not to wait for "permission" if a change was in patients' interests.
Mr Nicholson also highlighted the change in composition of his audience at a conference last week accompanying publication of the report. He welcomed the fact that at least a quarter of the 300 chief executives in attendance were representing alternative providers.