Private ambulances responded to more than 200 calls a month across the Bradford district on average last year, new figures have revealed.

The Yorkshire Ambulance Service NHS Trust confirmed that vehicles from providers such as St John Ambulance and the British Red Cross were assigned to 1,325 calls to addresses with a Bradford postcode during 2013, an average of 206 per month.

The busiest period was March 2013, when private ambulances were called to 393 incidents across the Bradford district, 5.5 per cent of the 7,193 calls made in total that month.

The figure had jumped from just 16 calls the previous month, February 2013, an increase of 2,356 per cent.

Unite the Union has expressed concern at the use of private ambulance firms to “plug the gaps” in NHS 999 responses, stating earlier this year that it believed the use of such vehicles was part of the Trust’s “unspoken strategy” of preparing the ambulance service for privatisation by the back door.

When asked to explain why the figures, obtained via a Freedom of Information Request, had fluctuated so markedly across the Bradford district, a spokesman for the Trust said: “When demand for our emergency service is particularly high, our own resources have in the past, at times, been complemented by St John Ambulance, British Red Cross and private ambulance service providers.

“Private ambulance crews were not assigned to a particular area. This gave the Trust total flexibility on their location and the ability to move crews about within a short space of time to specific areas requiring extra resource.”

Despite stating that the use of private ambulances was “common practice” among ambulance services throughout the country, the spokesman said the Trust was not “currently” using private providers in its emergency services.

In January this year, only 297 responses across Yorkshire had been assigned to private ambulances, 52 in the Bradford district. The figures for February and March were both zero, suggesting that private vehicles were no longer being used, although the Trust would not comment on how the services such vehicles had provided had been replaced.

“As a professional ambulance service we respond to the overwhelming majority of our emergency patients using our own staff and vehicles,” said the spokesman.

“Safeguards and operating standards are in place to ensure that the use of private ambulance services does not compromise patient safety, and the organisations we work with are all registered with the Care Quality Commission, the independent regulator of all health and social care services in England.

The figures also revealed that £2.8million had been spent on private ambulances across Yorkshire within A&E and Patient Transport Services between April and December 2013, an increase from £1.7million during 2012/13.