A new study shows that family doctors have been giving placebo drugs to their patients who thought they were getting an active medicine.

In a poll highlighted in the PLOS One medical journal, a staggering 97% of 783 GPs asked in Britain admitted that they had recommended a dummy pill to their patients.

But the authors say this may not be a bad thing as doctors are prescribing these pills to help, and not to deceive patients.

And while the Royal College of GPs says there is a place for placebos in medicine, they also warn that some dummy pills may be “inappropriate”, and could cause side effects or issues such as drug resistance.

About one in 10 of the GPs in the study said they had given a patient a sugar pill or an injection of salty water rather than a real medicine at some time in their career. One in 100 of them said they did this at least once a week.

Dr Jeremy Howick, co-author of the study that was carried out by the University of Oxford and the University of Southampton, said: “This is not about doctors deceiving patients. The study shows that placebo use is widespread in the UK, and doctors clearly believe that placebos can help patients.”

The so-called ‘placebo effect’ has been shown in trials to produce benefits for patients when they believe they are taking an active medicine, and supplementing sugar pills for real medicines for minor diseases has been a long established practice for doctors for many years.

Dr Clare Gerada, chairwoman of the Royal College of GPs, told the BBC it was “perfectly acceptable” to use a placebo as long as it did not cause harm and was not expensive.

“Lots of doctors use them and they can help people,” she said. “If you think about it, a kiss on the cheek when you fall over is a placebo.

“But there are risks. Not all of the placebo treatments that the researchers looked at in this study are inert. If you take too many vitamins, for example, some can cause harm.”

She said fobbing off patients with an ineffectual treatment was never acceptable. “But admitting to your patient that you do not know exactly what is going on, but that a therapy might help is.”