Writing in an accompanying comment, Dr Steven Nissen from the Cleveland Clinic said that the findings raise important questions about the safety of ARBs.

He urged pharmaceutical companies to provide regulators with complete trial data so that the possible link between ARBs and cancer can be investigated properly.

"In the interim, we should use ARBs, particularly telmisartan, with greater caution," Dr Nissen advised, adding that they should be reserved for patients who are unable to take another class of blood pressure-lowering drug called angiotensin-converting enzyme (ACE) inhibitors.

Martin Ledwick, head information nurse at Cancer Research UK, commented: "It's important that we try to understand all the side-effects of drugs so that people can make an informed choice about their treatment.

"At the moment there isn't enough evidence to draw any firm conclusions about how blood pressure drugs might affect cancer risk and this will need further investigation. People shouldn't stop taking these drugs on the basis of this research. If they're concerned they should speak to their GP."

Source: Cancer Research UK