"We believe there's no advantage over safer drugs, and we believe it should be withdrawn from world markets," said Dr David Henry, of the Institute for Clinical Evaluative Sciences, in Canada.
"Given the availability of safer alternatives, diclofenac should be delisted from national essential medicine lists," said study lead author Dr Patricia McGettigan, from the William Harvey Research Institute in London.
However, Medsafe said all medicines carried risks and benefits.
"In 2008 Medsafe reviewed the safety of non-selective, non-steroidal anti-inflammatory drugs (NSAIDs), such as diclofenac and concluded that the benefits of using diclofenac to treat pain and/or inflammatory conditions outweigh the potential risks for the majority of patients," said Medsafe Group manager Stewart Jessamine. He said Medsafe's advice for consumers was to use the lowest possible dose of diclofenac for the shortest time possible.
It was prescribed for 375,000 people in the year to November 2012.