The placebo effect is something many doctors seem to be hoping for when treating patients. But prescribing pills that won’t work, just to keep patients happy, is damaging modern medicine as we know it.

A survey has found 45 per cent of GPs admit prescribing antibiotics unnecessarily, despite knowing the drugs will not help. Ninety per cent of the doctors said they felt patients put them under pressure to give them the drugs.

They survey, attracting 1,004 responses from GPs, is published by organisers of the Longitude Prize, an award that will go to the creator of a cheap and simple test to show whether or not antibiotics are necessary.

The hope is that the system will help GPs, 70 per cent of whom said antibiotics were given when they could not tell if the patient’s illness was due to a bacterial infection or a virus.

The Longitude Prize hopes to find a diagnostic tool that will end that uncertainty within five years, to tackle the urgent problem of bacteria becoming immune to drugs due to widespread overuse of antibiotics.

The past 15 years have seen a dramatic increase in the amount of antibacterial medication being prescribed to people with low-level illnesses such as coughs and colds – the kind of afflictions that often just go away on their own.

Bacterial immunity is not entirely down to GPs prescribing antibiotics because of patient pressure or their own lack of certainty, but the tool sought by the Longitude Prize will go a long way to helping matters.

Longitude Prize leader Tamar Ghosh told The Guardian: “We recognise that stemming the misuse and overuse of antibiotics is just one piece of the jigsaw to slow bacterial resistance to antibiotics.”