An alleged drink driver has collided with a parked ambulance that had its emergency lights flashing and sirens sounding in suburban Adelaide.

Police say the 22-year-old man's car hit the ambulance on Marion Road at Plympton Park just after 2:00 am ACST.

They say the car crossed the median strip and struck the front fence of a home.

The Ascot Park man allegedly recorded a blood alcohol reading of 0.187.

He has lost his probationary licence and faces charges including drink driving.