More than a third of doctors in England think Boris Johnson's three-tier lockdown system will have no impact on curbing the spread of coronavirus.
A major survey by the British Medical Association laid bare concerns among medics about the effectiveness of plans that have plunged millions of people into tighter lockdowns.
The Prime Minister's three-tier plan - designed to simplify confusing rules around local lockdowns - has attracted criticism for inconsistencies between different regions.
And some critics have questioned whether it goes far enough - with Labour instead calling for a national circuit-breaker lockdown.
It comes amid reports ministers are considering a shake-up to the plans if they have not made a difference by mid-November.
A plan said to be being discussed in Whitehall is adding a "tier four", which could see closures of non-essential retail and restaurants.
A survey of more than 6,000 medics found more than a third (37%) felt the tiering system would have no impact or be ineffective against the virus.
Less than half (46%) of respondents said they thought they would work to a slight extent and only 5.95% said a significant extent.
The survey also found deep concerns among healthcare staff for the autumn/winter period, with more than half saying they are "quite anxious" about it.
Almost two thirds (65%) sounded the alarm over staffing shortages, while 60% said they are concerned about their personal health and wellbeing.
Some 58% said they are concerned about the ability to cope with demand from non-Covid patients, and 44% said they were worried about the ability to cope with demand from patients with Covid symptoms.
BMA chairman Dr Chaand Nagpaul said: "Doctors know that this winter is likely be one of the most difficult times of their careers.
"They are extremely worried about the ability for the NHS to cope and their ability to care for the needs of their patients."
He went on: "Large numbers of doctors across England have little faith that the Government's current 'tiered' based lock-downs will have any significant impact on controlling the virus.
"Instead of a few short weeks of suppression, bringing economic and emotional misery for those in the areas affected, we need a national prevention strategy that has a lasting impact and gets growing infection rates under control across England."
The BMA said it is calling for the Government to be "both honest and realistic with the public about whether the NHS can cope with routine care and Covid care this winter".
Almost a fifth (19%) of those questioned said in the two weeks leading up to the mid-October survey they had seen a significant increase in the number of Covid cases and it was higher than the same point in the first wave.
Some 11% said while their local health system has plans in place to be able to address the backlog of patients whose care was cancelled, delayed or otherwise disrupted amid the pandemic, they had not yet made any progress, while just over a quarter (27%) said they had made some.
Only around a third said they have premises that are currently suitable to adequately separate Covid and non-Covid patients - a statistic the BMA said highlights how difficult it will be to meet an expectation of resuming normal NHS services.
Some 6,610 doctors in England took part in the survey during the week of October 19.
A majority (70%) said they had not contracted coronavirus.
