The new study found that black patients previously diagnosed with high blood pressure were significantly less likely to achieve an established target for their blood pressure than white or south Asian patients.
On the other hand, South Asian patients with poorly controlled high blood pressure were prescribed fewer blood pressure lowering medications than their black or white peers.
White patients who had high blood pressure and also two or more cardiovascular problems showed significantly improved blood pressure control, but the same improvement was not seen in black or south Asian patients.
"It is worrying that differences in blood pressure control between ethnic groups have persisted, particularly in high risk patients, in spite of doctors focusing a lot of effort on this area of patients' health," said Dr Christopher Millett, the lead author of the study from the Division of Epidemiology, Public Health and Primary Care at Imperial College London.
"There are a number of potential reasons for the differences in blood pressure control found between white, black and south Asian groups.
"These include differences in how doctors treat these patients, differences in patient adherence to therapy, and biological differences in the response to antihypertensive therapy.
However, further research is required to better understand the reasons for these differences," Millett added.
The study is published in the journal Annals of Family Medicine.