The Chair of the British Medical Association says that claims that doctors can provide a "24 hour a day 365 days a year service are ridiculous".
Dr Mark Porter told delegates that the health service can barely afford its current model, and that plans for doctors to do more would only add to that burden.
"Like many of you I work nights and weekends as well, at times when much of the private sector is fast asleep and ministers are tucked up soundly in their beds" he said.
"We all want urgent care at weekends and evenings to be of the same high standards as patients can expect on weekdays.
"But the calls we sometimes hear for a Tesco NHS, full service, 24/7, are just ridiculous when the health service can barely afford its current model.
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