NHS hospitals are increasingly failing to meet the target for seeing A&E patients within four hours, according to new figures.
Data from more than 40 NHS trusts, published by the Royal College of Emergency Medicine (RCEM), showed 86% of A&E patients were treated or admitted within four hours as of December 4 - well below the 95% target.
The A&E target is widely regarded as a key measure of how the NHS is performing, especially in the winter months.
On November 20, the figure was 88%, and on November 13 it was 89%.
The RCEM's report said: "It is now clear that performance against the four-hour standard has declined steadily since the beginning of October.
"What this tells us is that despite the significant efforts made by trusts/boards to improve performance through winter planning, the system as a whole has struggled to maintain performance against a backdrop of rising demand."
NHS England has been criticised over its decision not to publish key weekly data - including performance against the A&E target - showing how NHS hospitals are performing over winter.
Experts said the move could hamper the way NHS trusts operate, while the public will also be unable to scrutinise the figures.
Official figures published monthly up until September showed that the target has largely been missed for the last year.
Nigel Edwards, chief executive of the Nuffield Trust, has said the decision not to publish could fail to highlight areas where the NHS is under excessive pressure.
Last year, Labour accused Health Secretary Jeremy Hunt of enforcing a "news blackout" by not publishing weekly A&E figures over the Christmas holidays.