YORKSHIRE Ambulance Service spent £364,000 in five months on sending private firms to answer 999 calls.
The organisation was forced to use private ambulances in response to emergency calls for the first time because of high demand.
Between last December and April this year, private ambulances were sent to more than 1,600 emergency call-outs in Yorkshire, according to figures released in response to a Freedom of Information request.
Most were in West Yorkshire but commercial firms also attended incidents in North Yorkshire, Humberside and South Yorkshire.
The move comes as all health bodies are forced to save 4 per cent of their budget each year.
George Mudie, Labour MP for Leeds East, said the spending was “staggering”.
“It also begs serious questions about why they themselves cannot meet demand for emergency responses over the winter months.
“I think it is basically privatisation by the back door.”
David Williams, deputy director of operations for Yorkshire Ambulance Service NHS Trust, said they would always prefer to use their own staff and vehicles.
“However, when demand for our services is particularly high, our own resources can be complemented by private ambulance service providers,” he said.
“This is common practice amongst ambulance services throughout the country.”
He said between December 2011 and April 2012, the service attended 287,289 emergency incidents – 0.6 per cent of which were answered by private ambulances.
All providers were registered with the Care Quality Commission, he added.