The data for January from NHS England showed 88.7% of patients were dealt with in four hours. The target is 95%.
That is the worst monthly performance since the target came in in 2004.
NHS England blamed rising demand - overall attendances were up by more than 10% compared with the same time last year. There was also a sharp rise in emergency admissions and calls to NHS 111.
Richard Barker, from NHS England, said: "Against this backdrop it's not surprising hospitals saw a dip in their performance and it is credit to all those working in emergency care that we are still admitting, treating and discharging almost nine in 10 patients within four hours
"Winter pressures have come late this year with a sustained cold period and an increase in seasonal infections."
During January the BBC reported how hospitals were being forced into taking extreme measures to cope.
Some cancelled routine operations en-masse, while there were reports of GPs being advised not to cut back on hospital referrals and emergency treatment areas being set up outside A&E units.
The monthly performance publication also showed the NHS was struggling in other areas:

Speaker Mitchel McLaughlin said Gregory Campbell had been "blatantly disrespectful" after he yawned loudly twice when Sinn FÃ©in member Caitriona Ruane had been speaking in Irish.
It happened last Monday.
Mr Campbell was barred from speaking on Monday and Tuesday.
"It can be tiring listening to Sinn Fein abusing the Irish language," said Mr Campbell.
"Has Caitriona Ruane nothing else better to do with her time than complain?
"Does this mean every time you blow your nose someone is going to say that's inappropriate nose blowing?
"This is ludicrous. It's nonsensical.
"If I was feeling somewhat tired I would yawn in Westminster too.
"Some people yawn quietly, some yawn loudly."
Last November, Mr Campbell was barred from addressing the Northern Ireland Assembly for a day for failing to apologise for an Irish language parody.
A row developed after he began his address to the assembly with: "Curry my yoghurt can coca coalyer".

Yvonne Kershaw, a 64-year-old grandmother from Petworth in West Sussex, landed the Virgin Atlantic flight from Cancun in Mexico.
Mrs Kershaw joined the airline in 1990 and was granted command of the Boeing 747 aircraft three years later.
She said it had taken passengers a few years to get used to seeing a woman coming out of the flight deck.
"I suppose normally they would expect to see a silver-haired fox flying the aeroplane in command," she added.
"Breaking down those barriers wasn't easy but nobody ever said it would be.
"What you need is passion about your job, determination and skill."
Mrs Kershaw learned to fly at the age of 19 and after flying small aircraft around Europe and north Africa she gained her commercial pilot's licence and flew executive jets.
When she joined Virgin Atlantic its fleet included only four 747s.
"It's such an iconic aeroplane and it's what I wanted to fly. For decades it was the largest aircraft in the world and the most loved by everybody," she said.
Mrs Kershaw has captained more than 2,000 flights with more than 18,000 flying hours in the jumbos.
She said she was "slightly tearful" after landing her final flight and would miss the role "enormously".
"With long-haul it's not a job, it's a way of life, because you spend so much time away from home with crew. They become part of your extended family."
A&E delays in England have reached record levels, official figures show.
[NEXT_CONCEPT]
DUP MLA Gregory Campbell has defended his actions after being barred by the assembly speaker over what has been described as "schoolboy behaviour".
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The UK's first woman jumbo jet pilot has retired after landing at Gatwick Airport for the last time.