Screening for prostate cancer does not save lives, and may do more harm than good, a major study has concluded.

The largest ever trial of PSA (prostate specific antigen) tests - which all men over 50 can obtain on request from their GP - found that death rates were identical among men, whether or not they underwent screening.

Inviting symptomless men for the one-off blood test detects some tumours unlikely to be harmful - while still missing others that were fatal, researchers warned.

The study, funded by Cancer Research UK, follows a long debate about whether the NHS should introduce routine screening, using the tests.

Lead author Professor Richard Martin, a Cancer Research UK scientist at the University of Bristol, said: "Our large study has shed light on a highly debated issue.