The results were obtained under the Freedom of Information Act. They represent the first published evidence of the extent of the prison drug problem and will prove embarrassing for the Government.
The new data reveal no reduction in drug consumption in prisons since the launch in late 2004 of the Government's drug-free prison policy. The number of tests carried out has actually fallen since the policy was launched.
Most of those inmates who tested positive across the system were positive for a cocktail of drugs. Some 33,779 of the positive tests were for cannabis, 26,584 for benzodiazepines, 25,346 for opiates, 2,017 for cocaine, 850 for alcohol and 620 for amphetamines.
There are 3,200 inmates in prison at any one time, with about 10,000 committals every year. Many inmates are tested for drugs more than once per year.
The rate of positive tests across the prison population has remained at about the same levels in the past three years. Of the 25,362 tests carried out in the first nine months of last year, 36 per cent were positive for traces of banned substances.
In 2006, 25,276 tests were carried out, with 37 per cent giving positive results. In 2005 some 37,288 tests were carried out, with 47 per cent testing positive.
The higher percentage rate of positive tests in 2005 is attributable to the fact that 8,300 more tests were carried out at Mountjoy Prison, Dublin, that year than in 2006.
Conor Lally, Crime Correspondent