The Coast Guard spent hundreds of thousands of euro on 18 vans that cannot carry a full rescue crew and all its equipment at the same time.
Crews have been critical of the vans because weight limits restrict the number of personnel or equipment they can carry.
Officials bought the 18 Ford Transit-type vans before adapting them to cater for the unique specifications its climbing units need.
Coast Guard climbing crews use vans to carry vital rescue equipment and gear to scale dangerous cliff faces. The vans are also used during rescue missions as mobile communications units and search vehicles.
The vans come as standard with seven seats and four-wheel drive capability, but the Coast Guard fitted and adapted them.
This work saw two seats removed from each van so the vehicles could carry a five-person crew. Panelling, storage systems and climbing equipment were all added.
Each of the vans can carry 3,500kg. However, by the time the fitting was completed each van was within 84kg of the maximum capacity weight, meaning the vans could only carry a driver and no passengers or crew.
Academic studies show the average weight of a European adult is 71kg.
Coast Guard crews say the vehicle weight issue is problematic.
"It means we can't really use the van for the purpose intended. Do we carry all the gear? And if not, what do you sacrifice?" a source told the Sunday Independent.
"If the van is full and weighs too much, that obviously creates a problem with going on bad surfaces."
It comes after the Sunday Independent highlighted concerns about Coast Guard life jackets and how its drivers have been confused about using emergency blue lights and sirens.
A spokeswoman for the Department of Transport, which is responsible for the Coast Guard, said a fleet replenishment programme is under way.
She said this will cater for the varying needs of Coast Guard crews.
The 18 vans initially purchased for the climbing crews are now set to be redeployed elsewhere within the agency.
"The Coast Guard operates a fleet of response vehicles located around the coast," she said.
"Within the fleet are 18 vans which are fitted out for transporting response equipment. These vans are designed to carry equipment suitable for cliff rescue and shore response.
"Given the requirement to transport additional equipment - first aid equipment, flare storage bottles, mule wheels used to transport stretchers, navigation equipment, signage, lighting, life jackets, etc - these vehicles will now be deployed operationally in support of drone units and as incident support vehicles."
She said the ongoing fleet replenishment would cater for transporting personnel, towing, launching boats, moving cliff rescue gear and off-road or shoreline search equipment.
"Irish Coast Guard will continue to resource units with appropriate vehicles to maximise operational efficiency."
Last month the Sunday Independent highlighted how there was "no clear direction" about the use of "fitted blue lights and warning devices" on Coast Guard vehicles.
Crews have also expressed concern about sharing life jackets after senior officials ignored the advice of a major supplier and took its old buoyancy aids out of operation.
They said this has curtailed rescue operations because each station can only deploy one lifeboat at a time due to the limited number of available life jackets.