Nearly half of doctors (48%) fear they could not cope with a second wave of COVID-19 cases according to a poll of BMA members that received 7,268 responses.
Doctors' leaders said this was 'not the time to be complacent' around easing lockdown, warning that official statistics continue to show 'significant community spread of the infection'.
The warning came as updated government advice that relaxes guidelines for the public took effect - with changes including groups of up to six people from different households now being allowed to meet outdoors as long as social distancing is maintained.
Patients in high-risk groups told to shield have also been told they can now go outside - and if they live alone, meet one person from another household at a 2m distance - in changes brought in without consulting GPs.
BMA chair Dr Chaand Nagpaul said: 'As the government relaxes lockdown measures, we absolutely must not forget that the infection rate in the community remains worryingly high.'
Citing Office for National Statistics data showing '8,000 new cases daily', the BMA chair warned that the risk from COVID-19 'remains significant'.
He added: 'That is why it’s vital that we have a fully functioning system of test, trace and isolate running seamlessly now with full transparency.
'Of course, as doctors we understand the impact that lockdown has had on people’s health and wellbeing and how eager people are to return to some semblance of normal life. But this must be done gradually and sensibly, and the government must also take every measure possible to support the public and employers in stopping the spread of the virus, whether that’s in outdoor places, reuniting with friends and loved ones, or returning to work.
'Doctors have been working tirelessly during the pandemic to care for patients and save as many lives as possible, putting their own safety, health and wellbeing at risk. And as we sadly know all too well, many have already lost their own lives in the fight against this deadly virus
'Doctors working on the frontline are therefore rightfully worried about the devastating impact a second peak could have for their patients, the health service and the wider population. This is not the time to be complacent.'
A Cabinet Office spokesperson said: 'The government has been very clear that any easing of lockdown measures has to be done slowly and cautiously to avoid a second peak of the virus that could overwhelm the NHS.
'Thanks to the efforts of the public, the government’s five tests are now being met, which means we are making small steps towards the next phase of lifting the lockdown.
'The new NHS Test and Trace service is up and running and will help us to keep the virus under control as we continue to make progress.'
Commenting on changes to shielding guidance, a DHSC spokesperson said the government had 'engaged extensively with partners and the healthcare system' throughout the pandemic.
The spokesperson added: 'We want to make life easier for the most vulnerable and, as the number of COVID-19 cases continues to fall, the evidence shows those shielding can spend time safely outside if they wish, as long as they follow social distancing guidelines.'