East Midlands Ambulance Service (EMAS) said they responded to a genuine emergency in Leicester, during which a note was put on the windscreen.
The handwritten note said the ambulance had been blocking the neighbour's driveway for 45 minutes but EMAS said the vehicle was parked "as considerately as possible".
The service has now asked for anybody with a problem to speak to them directly if they urgently need to leave their house and their access is blocked.
In March, Yorkshire Ambulance Service revealed details of an angry call in which staff were asked to move their ambulance while treating a patient with a life-threatening condition.Lee Brentnall, Paramedic and Ambulance Operations Manager for Leicestershire said: "It is so disappointing to see that a rude note has yet again been left on one of our ambulances.
"This upsets our dedicated ambulance crews when they are trying to help our patients and do their job.
"Leaving a note will not resolve the situation as we are unlikely to see it until we are leaving in the ambulance to take the patient to hospital or to go to our next job."
Ms Brentnall continued: "Our crews are approachable. If you genuinely need to leave your house urgently and we are blocking your access, please come and knock on the door where the emergency is taking place.
"Sometimes we will be able to move the vehicle, for example if we are treating a patient but they do not need both of us there at the time.
"However, there will be times that we are treating someone experiencing a life-threatening and time-critical emergency and moving our ambulance will not be our priority.
"In these cases, you will need to be patient as we try to save someone's life."