A Freedom of Information (FoI) request from the BBC has revealed Essex Police cars were regularly used by the East of England Ambulance Service to take patients to hospital in 2013.
Figures released by NHS England show that there were 185 occasions where staffing or ambulance shortages led the police to have to cover for stretched paramedics.
This has angered police chiefs, who argue they are already faced with extensive budget cuts without having to manage the needs of another emergency service.
The worst month for this was March, when there were 22 occasions where no-shows or "excessive ambulance delays" led to the police being called out to take people to hospitals.
It is not clear if any of these cases led to death or the furtherment of serious injuries, but a statement released by the East of England Ambulance Service claimed it needed more staff and could not cope with high levels of demand.
One of the biggest problems for the East of England authority is that many patients reside in rural areas that can be hard to reach within target times, meaning the police have to step in when ambulances cannot attend.
A spokesperson for the ambulance service said: "We recognise we do not currently have sufficient ambulances to respond to all emergency calls as quickly as we need to.
"Be assured that our staff are already working as hard has as they can, but we simply need more of them in order to improve our response times.
However, a representative from Essex Police urged quicker action and relayed his concerns that "increasing demand from the ambulance service" is stretching the force's already thin resources close to breaking point.
"We monitor incidents of this nature closely and it is correct to say that incidents have increased slightly over the past 12 months," the spokesperson added.
A number of MPs in rural constituencies, including secretary of state for care Norman Lamb, have campaigned for better funded ambulance services in recent months.