Dr Chaand Nagpaul, chairman of the British Medical Association's GP committee, said the system could add to pressures on hospitals, rather than reduce them. "Owing to the lack of input from a trained professional, this simplistic system could, like NHS 111, result in more people being sent to overstretched GP or A&E services who don't actually need treatment - or conversely serious conditions being missed," he said. Peter Walsh, chief executive of safety campaign group Action Against Medical Accidents, questioned who would be liable if computer error caused patient harm or death. "The NHS 111 algorthym has already proved prone to error - that risk could be even greater under a system like this," he said, calling for robust evaluation of the six-month scheme. Katherine Murphy, from the Patients Association, said: "The stakes here are very high, I would be concerned about the risks to patient safety; this needs to be very carefully evaluated because of the risks of misdiagnosis."

At the end of the exchange, the app will advise a patient on how to proceed, an alternative to the advice of 111 call-handlers who are able to send ambulances, book an out-of-hours doctor or suggest other treatment. The trial is seen as a potential solution to the strain on the 111 service. Interactions with the app are significantly cheaper and quicker than speaking over the phone. It is hoped that the database of medical information that Babylon has could mean more effective advice than the 111 staff who are not medical professionals, although many users may have misgivings about the effectiveness of medical advice from a chatbot.