Almost half of GPs have admitted prescribing antibiotics even though they know they will not treat the patient’s condition, a survey shows.

Ninety per cent of doctors who responded to a recent questionnaire said they felt pressure from patients to hand out the medications.

The Longitude Prize survey compiled responses from 1,004 GPs across the UK and found 28 per cent prescribed antibiotics several times a week, even when they were not sure if it was medically necessary, and 45 per cent had done so knowing they will not help.

The findings come after experts at Public Health England and University College London revealed earlier this month that the number of patients given antibiotics for minor ailments has soared in recent years.

Between 1999 and 2011 the proportion of patients given antibiotics for coughs and colds soared from 36 per cent to 51 per cent, the study published in the Journal of Antimicrobial Chemotherapy found.

Last month, prime minister David Cameron said antibiotic resistance was a “very real and worrying threat” as he pledged to put Britain at the forefront of the fight against drug immune bacteria threatening to send medicine “back to the dark ages”.

The latest research comes ahead of the £10m Longitude Prize which will open for entries later this year to find an easy, cost effective test for bacterial infections that doctors can use to determine if and when to give out antibiotics.

Seventy per cent of GPs surveyed said they prescribed because they were not sure whether the patient had a viral or bacterial infection, and 24 per cent said this was due to a lack of easy to use diagnostic tools.

Tamar Ghosh, who leads the Longitude Prize, said accurate diagnostic tools could help curb unnecessary use of antibiotics across the globe.

“In the next five years the Longitude Prize aims to find a cheap and effective diagnostic tool that can be used anywhere in the world,” she said.

“We recognise that stemming the misuse and overuse of antibiotics is just one piece of the jigsaw to slow bacterial resistance to antibiotics.

“Nevertheless, it’s an important step when we could be waiting many years for other solutions.”

Just 6 per cent of 1,074 patients surveyed by Populus earlier this month said they would push their GPs to give them antibiotics, despite the high number of doctors saying they feel under pressure to do so.