Doubts
Professor Neil Poulter, an expert in cardiac medicine at the National Heart and Lung Institute, told the BBC News website that there had been doubts about the effectiveness of atenolol for some time.
He said it was possible that the drug increased blood sugar levels, or had an adverse effect on cholesterol.
He said the National Institute for Clinical Excellence recommended a combination of beta blockers and diuretics to treat hypertension.
However, the British Hypertension Society had concerns that the combination could increase the risk of diabetes.
Professor Poulter said a major trial of 19,000 patients was underway in which the beta blocker/diuretic combination was being compared to another combination of drugs - an ACE inhibitor and a calcium channel blocker.
However, he said there was no reason at this stage why people who were taking beta blockers should stop their medication.
“There a very good reasons why patients should not suddenly stop taking beta blockers. If they were to stop then it should be done gradually and under the close control of a physician.”
The drug was originally developed by drug giants AstraZeneca, whose patent expired in 1991.
A spokesman for the company said: “We believe that this study is inconclusive.”