Spending on private ambulances by local hospitals including Mid Ulster and Antrim has increased by tenfold in the past five years, the second highest increase in Northern Ireland.
Last year, the Northern Board spent a total of £125,000 on private ambulances compared to just £12,000 in 2009/10. The bill has been markedly increasing each year.
The figures were released by the Department of Health last week at the Northern Ireland Assembly.
Critics have claimed that the surge in expenditure proves that the ambulance service is at risk of being completely privatised and runs the risk of improperly trained staff.
Senior medics and safety campaigners said they fear patient safety is being jeopardised by a heavy reliance on commercial firms to answer emergency calls.
SDLP MLA for Mid Ulster, Patsy McGlone, has expressed concern at the huge increase.
“At a time when the Department of Health’s budget is under severe pressure there are serious questions about how the increased use of private ambulances provides value for money in the long term”, he said.
“I will be seeking answers from the Health Minister about the awarding of these contracts and whether this represents a departmental policy of increasing privatisation of our Health Service.”
UK ambulance trusts said they had little choice, warning of a “national shortage of paramedics”.
The figures were revealed last week by the Department of Health at the Northern Ireland Assembly.
The Western Board had the biggest increase in private ambulance use rising more than twentyfold from £12,000 in 2009/10 to £215,000 in 2014, while the use almost quadrupled in the Southern Trust area.