Concerns have been raised over the lack of ambulance back-up after almost 70% of emergency cover was not met in a six-month period.
The Northern Ireland Ambulance Service (NIAS) in the Northern Trust area struggled to fulfil its planned cover from November 2016 until April this year.
During that period of 181 days, there were 121 days of no emergency back-up.
Stations in the Northern area with one full-time ambulance include Ballycastle, Ballymoney, Carrickfergus and Cookstown.
It has also emerged that on one day in December last year, five ambulance shifts were not covered.
The figures were revealed in a Freedom of Information (FoI) request by DUP MLA Gordon Lyons.
The East Antrim representative described the numbers as "startling".
"These figures will rightly be met with a mixture of outrage and concern," he said.
"The NIAS has effectively confirmed that 67% of planned cover from November 2016 to April 2017 was not achieved.
"This means that many of our towns were without any ambulance cover for a significant period of time.
"Our ambulance staff work exceptionally hard in very difficult circumstances, but clearly this situation is not sustainable in the long-term.
"It is imperative that those holding up the formation of an Executive get back around the table so that we can address this issue and give our community the confidence it requires in our public services."
The NIAS said that if the remaining resources are strained or unavailable, it operates a patient-centred, tactical deployment plan.
A NIAS spokesman said: "This is developed from and based on historical data on levels and nature of ambulance activity to ensure, as far as possible within available resources, that NIAS emergency personnel are best positioned to provide the most appropriate response in the shortest possible time.
"Therefore, to fill any gaps NIAS look at this historical data and move resources from a place of predicted less demand to that of more demand.
"This ensures that resources are in the best suited to location to respond in the shortest time frame."
The FoI request further stated that on most occasions the ambulance back-up related to one or two shifts not being covered in the Northern division on a daily basis.
"At all times the nearest available ambulance will be despatched to attend emergency calls with vehicles tactically deployed by the Emergency Ambulance Control in local divisions as required," the spokesman added.
In a separate statement, the NIAS said that in the Northern Trust area it planned to provide between 17 and 19 emergency ambulances per day and 12 ambulances each night for the period between April 2016 to March this year.
"NIAS achieved an average of 91.5% compliance with planned shifts," it added.
"NIAS is currently engaged in a review to determine increasing demand trends for its services and the capacity required to meet that demand."