Of the 29 drug units in the country, 19 have seen reductions in numbers and, in one case, in Cavan/ Monaghan, the unit has been disbanded altogether.
Four units have kept their strength while six units have managed to secure increased staffing levels.
Figures gathered by the Irish Examiner show that units worst affected are:
* Kildare: Numbers have fallen from six in 2009 to just one in 2011 (a drop of 83%);
* Wicklow: The strength of the unit has slumped from 11 to three (down 73%);
* Laois/Offaly: Numbers have fallen from 10 to three (down 70%);
* Wexford: The strength of the unit has dropped from 13 to five (down 63%);
* Meath: The numbers decreased from 10 to five (down 50%).
The Monaghan/Cavan unit had 11 detectives in 2009. Last January, the Irish Examiner reported that the unit had been disbanded altogether and that the five detectives still in it were being redeployed.
Half of the six Dublin units have been cut, two of them very significantly.
The Dublin Metropolitan Region (DMR) South Central unit had its strength cut from 19 to 13. This unit covers the south inner city, home to a number of major drug gangs, some of whom are engaged in violent feuds.
The DMR West unit had its numbers cut from 37 to 27. This unit covers a huge geographical area, from Blanchardstown and Finglas in the north to Clondalkin and Ballyfermot in the south. These areas are home to some of the biggest, and most violent drug trafficking gangs in the city.
The units in Cork City and Cork North are among those who have seen a rise in numbers, while numbers in Cork West have fallen.
The strength of the Garda National Drugs Unit — which targets gangs importing drugs into the country and distributing them — has fallen from 59 to 56.
The sharp cut to drug units is directly connected to the reduction in Garda numbers in recent years.
Earlier this month, Garda Commissioner Martin Callinan said 1,200 members had retired from the force since the introduction of a public service recruitment embargo in 2009. He said the overall strength now stood at 13,300.
He predicted the size of the force will fall below 13,000 later this year — a level at which he said there would be difficulties maintaining existing policing services.
The fall is placing massive pressure on dedicated Garda units as local commanding officers have to fill a hole in core policing.