An over-the-counter painkiller used by millions can significantly increase the risk of a heart attack or a stroke, research has found.

Patients using diclofenac were found to be 40 per cent more at risk than those who were not using the drug, a study published in Plos Medicine found.

Researchers from the Hull York Medical School and the Institute for Clinical Evaluative Sciences in Canada made the observation about the drug after they analysed 51 international studies into the impact of a range of NSAIDs on more than 2.7 million patients.