The NHS has recorded its worst A&E waiting times in England since current targets began in 2004.
The latest figures show that 83.6% of patients were seen within 4 hours in October.
That compares to 85.2% in September, and 89.1% in October 2018.
However, attendances rose to 2,170,510 in October, 4.4% up on the same month last year.
There were also 563,079 emergency admissions, a rise of 3.1%.
The 95% target in A&E was last met in July 2015.
Responding to the latest fugures, the Nuffield Trust said the next government would be faced with "one of the bleakest winters in the NHS's history".
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The health think tank added that there were "many months to go until seasonal pressures really hit the NHS".
Analysing the figures, it said: "The health service is seeing far more patients, yet one in six is now waiting more than four hours in A&E. If the usual trends continue after Christmas, that would head towards one in five."
Labour's shadow health secretary, Jonathan Ashworth, said the NHS was "in crisis" and a "winter of abject misery for patients" was in prospect.
He added: "Our A&EsRead More – Source