The £2.5m satellite navigation system allows the dispatch room to send information more quickly to crews, but implementing the service has led to delays.

Since July, only 66% of crews have reached the scene within the eight-minute government target, instead of 75%.

Phil Morris of East Midlands Ambulance Service said: "It is a situation we realised could happen when the new computer system was installed."

Major leap

He defended the recent drop, saying: "It is inevitable that when new systems are installed, there is a short period of disruption as we transfer to the new one."

"Occasionally in life it is necessary to take a small step back to make a major leap forward."

You need to think twice before you call for an ambulance

Phil Morris East Midlands Ambulance

Mr Morris said standards are picking up again and the service should be hitting its targets within the next three or four weeks.

The East Midlands Ambulance Service had similar delays when it introduced the same computer system in Nottinghamshire and Leicestershire.

The satellite navigation system sends information from the control room to vehicles more quickly, but installing it and learning the new procedures has caused some delays.

Mr Morris said another reason for the poor performance figures was the high number of time-wasting calls.

"You need to think twice before you call for an ambulance, as calling about minor problems like a splinter in your finger or earache will only prevent us from getting to more major calls."