NHS England is said to be in favour of ditching the standard for 95 per cent of patients to be admitted, transferred or discharged within fours in the next 12 months.
The move could see new targets introduced for the treatment of serious conditions like heart attacks and strokes.
People with less serious conditions might have to wait longer, although NHS trusts around the country are already seeking to divert non-emergency patients to urgent treatment centres.
Taj Hassan, president of the Royal College of Emergency Medicine, said any changes to the A&E target must have the support of medics. He said: “The four-hour emergency care standard is a remarkable totemic standard that is now deeply ingrained in the very fabric of NHS culture and process. It has very many advantages and some limitations.
“Attempting to make such change at such pace and without due regard to expert evidence is doomed to result in significant unintended consequences.”
NHS England figures show that in January, just 84.4 per cent of patients were seen in four hours at hospitals in England, the worst performance since records began.
Calls have been made for staffing levels and a lack of community beds to be addressed to help tackle A&E overcrowding.
Dr Hassan, who is a Leeds A&E doctor, said: “Moving the goalposts of measurement to make things seemingly look better is certainly not the way forward.
“Any attempt to impose a set of standards upon NHS emergency department staff that are not clinically appropriate, thoroughly tested or do not have the support of doctors, consultants, nurses and all other employees working in this environment will have a significant risk of critically destabilising a substantial number of systems that are struggling to maintain safety.”
NHS England said no final decision had yet been made and any changes would be tested before being implemented from October.