Almost a quarter of all deaths in England and Wales are potentially avoidable, 2014 figures released by the Office for National Statistics suggest.
The report shows that out of some 116,000 avoidable deaths in total, more than a third were caused by tumours.
And levels of avoidable deaths were significantly higher in Wales than in England. In England, the North East had the worst rates.
Department of Health officials say they are investing to tackle the issue.
The review looked at deaths that could have been prevented through good quality, timely healthcare or healthier lifestyle choices and public health interventions.
It suggests in 2014 there were 108,491 potentially avoidable deaths in England and 7,428 in Wales – 23% of all deaths that occurred that year.
And second to tumours, heart disease and strokes contributed to the most deaths.
The report found males had a higher proportion of avoidable deaths (29%) than females (18%).
Meanwhile for children and young people, almost a third of all fatalities (1,443 deaths) were considered avoidable. Nearly 200 were because of accidental injuries.
Commenting on the figures, Dr Anne Campbell of the ONS said: “People who die prematurely from avoidable causes lose an average of 23 potential years of life.
“For children and young people, this figure rises to 72 years.”
Meanwhile, England’s Department of Health said: “We want to cut all avoidable deaths to help people live better and for longer.
“That’s why we’re investing up to £300m a year by 2020 to improve earlier cancer diagnosis, and an additional £150m for a dementia research institute to help fulfil our goal to find a cure.
“Through campaigns we are also encouraging people to lead healthier lifestyles.”
And a Welsh government spokesperson said: “This is high on our agenda, and the benefits can be seen in the data from the recent Welsh health survey which show adult smoking prevalence reducing to 19%, and a small decline in alcohol use among younger adults.
“Wales is the only place in the UK to review every death in hospitals, and we are seeing success with measures to tackle sepsis, C. diff and MRSA.
“Every avoidable death is a tragedy, and we are working hard with NHS Wales to reduce avoidable mortality rates.”