The National Ambulance Service Representative Association said the service is under-resourced and "running on empty".
NASRA said there are insufficient personnel or vehicles to adequately meet response times demanded by the Health Information and Quality Authority.
HIQA has set a target for the National Ambulance Service to reach 85% of call outs within seven minutes and 59 seconds.
The Oireachtas Health Committee is today discussing recent cases involving delayed responses to incidents.
Michael Dixon, the NASRA National Chairman, said there are gaps in the provision of ambulance services across the state.
"[They are] mainly due to base closures, non-replacement of absent personnel, whole-time equivalent posts not being filled, and lack of investment across the services," he said.
"Over the past number of years, the cuts to budgets have seen a remarkable decrease in investment in the provision of pre-hospital emergency care."