Several Garda districts are without key senior officers because of a recruitment freeze, representatives have warned.
Superintendent Jim Smith, president of the Association of Garda Superintendents, said 21 top roles left empty or soon to be vacated were critical to the effective running of the force.
"I will be calling on the Minister for Justice to fill these vacancies immediately," he said.
"There are a number of operational districts being run at present without a superintendent."
Supt Smith said there are 11 vacancies at superintendent rank already and that will rise to 16 by the end of the year through impending retirements.
"Superintendents are central to the organisation in a district and it is very important for the efficient running of the district that a superintendent is in charge," he added.
There are currently 168 superintendents in the force.
More than 90 of these have completed 30 years of service and can retire.
As well as the 16 vacancies by the end of the year, the workload of another five posts has been handed to other superintendents or lesser-ranking officers to do, said Supt Smith.
Lesser-ranking officers are not allowed to perform certain statutory duties - such as dealing with prisoners - so some districts are forced to call in senior officers from other areas when needed.
"We want the planning for filling these vacancies to begin immediately," said Supt Smith.
Former Finance Minister Brian Lenihan ordered a ban on all public sector recruitment and promotions in March 2009.