The hospital grounds have been a smoke-free zone since 2006 – but it hasn't stopped some patients and visitors trying to have a sneaky smoke.

Now, anyone caught smoking on the site will be given a yellow card and asked to stub out their cigarette.

The card reminds them to be considerate of other hospital users and not force them to breathe in secondhand smoke. It also has advice on local stop smoking services.

The yellow card scheme to protect the health of staff and patients began on Wednesday to coincide with national No Smoking Day.

Consultant physician Dr Colin White said it was his duty as a doctor to advise smokers to quit for the good of their heath but nobody was forcing them.

He said: "We want to ensure our hospitals are healthy places for patients, visitors and staff. We're simply asking people to leave the hospital grounds before lighting up, or to stub out their cigarette before coming in."

Patient Bev Dawson has regular treatment at the hospital for progressive bronchiectasis, a genetic irreversible lung disease.

Ms Dawson, 45, said: "I come into hospital once a month for my care and have to walk though clouds of smoke – which just isn't fair.

"When I walk through smoke, I literally have to hold my breath as it irritates my lungs and exacerbates my infection.

"Hospitals should be a place to make you well and you shouldn't have to walk through that. I think the new cards are a really good idea."