NHS England has been accused of trying to abandon key targets because they can no longer be met.
A series of pilots were announced by the body last week, which could lead to significant changes including the scrapping of a target to see all A&E patients within four hours.
Some NHS trust chief executives said there was a lack of consultation on new measures, which will be tested this year and may be rolled out more widely afterwards.
Under the new plans, patients in England with the most serious conditions would receive rapid treatment within an hour, while people with minor conditions could expect to wait longer.
“There was a lot of work done to provide the evidence basis for four hours, and personally I think we are getting rid of it because it can’t be met anymore,” an NHS trust chief executive, who spoke on the condition of anonymity, said.
“If the central team really think that right now, anybody who is critically ill does not get seen within the right time in order to enable them to have the best outcome possible, I think they have lost touch with what actually happens on the front line.”
Ahead of the announcement, the Royal College of Emergency Medicine warned that scrapping the target would have a “a near-catastrophic impact on patient safety”.
Referring to the warning, the trust chief executive, said: “We may well be seeing the start of a direction of travel where NHS England make decisions about clinical standards without proper consultation with the professional bodies and the clinicians on the ground, who actually know how services are delivered.”
The four-hour target has not been met since July 2015, and latest A&E data shows that only 84.2% of patients were seen in four hours in February, the lowest proportion on record.
Another NHS trust chief executive, who did not wish to be named, said it was a “marker of a hospital working well”.
“My trust can’t meet the standard anymore, the reason we can’t meet it is workforce issues,” they said.
“That doesn’t mean abandon the standard, that means let’s focus on workforce.”
Saffron Cordery, deputy chief executive of NHS Providers, said: “Targets have played a crucial role in reducing delays and contributing to safe high quality care.
“That’s why targets matter to trusts, and it’s why they work so hard to meet them.
“It’s right to look at whether the targets we have are clinically relevant and work in the best interests of patients and service users, treating those most unwell most quickly while ensuring everyone has access to timely care
“But we need to ensure if we change them we’re doing it for the right reasons, backed by a clear clinical consensus based on strong evidence.
“By all means let’s look at different approaches that could improve care.
“But it would be wrong to make changes simply because the service is struggling to deliver existing targets. We must make changes based on testing, evidence and consultation.”
The four-hour standard is among a series of targets for A&E, cancer patients and planned operations which could be changed.