The Department for Transport publishes Reported road casualties in Great Britain: Estimates for accidents involving illegal alcohol levels which provides estimates of casualties arising from reported accidents involving at least one motor vehicle driver or rider over the legal alcohol limit for driving
Figures are derived from the STATS19 forms completed by the police plus toxicology data for road fatalities from coroners and procurators fiscal.
These statistics, especially the number of fatalities, are subject to considerable uncertainty which means that it is impossible to be sure of the precise number of casualties, so ranges and confidence intervals are used.
A drink-drive accident is defined as one where someone is killed or injured, and either one or more drivers involved either failed a roadside breath test, refused to give a specimen or died within 12 hours and was found to have a level of alcohol in their blood.
More information on these tests and the differences in the allowable limits between England, Wales and Scotland can be seen in the source report.