East Midlands Ambulance Service (EMAS) has issued a "polite notice" to motorists after a car was parked so close to an ambulance that crews were unable to access the vehicle.
The incident happened last week when crews were treating a patient in Nottinghamshire.
In a tweet, EMAS said: "Polite notice: sometimes we need to open our back doors to take patients inside who may be on a stretcher.
"Unfortunately, one of our crews, last night, went outside to discover this is how their patient's neighbour had parked next to them, making this impossible."
EMAS said the patient was treated at home but issued a plea to drivers to think carefully about where they park.
David Whiting, Chief Operating Officer for East Midlands Ambulance Service, said: “I would ask all motorists to think carefully about how they park near any of our ambulances or emergency response cars.
“Leaving vehicles where they could hinder access or delay our teams from getting a patient on the ambulance could have potentially disastrous consequences in a life-threatening emergency, often where every second counts.
“I would also like to remind drivers to park considerately and never leave their vehicle in a position where they could prevent emergency vehicles getting through to the scene of an emergency.”
The post provoked an angry reaction on Twitter, with many people calling for the person responsible to be named and shamed.
Mike Wall said: "Name and shame them, the lack of respect for all our emergency services is getting worse..... How sad."
And Dave Hughes commented: "Doesn’t this just make you cross and full of disappointment, again I hope they or their loved ones are never in need of an ambulance."
Clair Raybould said: "Awful, not only mean to neighbour and staff could risk another life if it took crew longer to sort it."