Emergency services were called to Coneyhurst Road around 11.20pm on Sunday (May 2) to a report of a white Ford Kuga leaving the carriageway and colliding with a tree and a fence, police said.
A spokesman added: “The driver, a man in his 20s, was taken to the Royal Sussex County Hospital in Brighton for treatment to serious injuries. He is now in a stable condition.
“Officers investigating the collision are keen to speak to anyone who saw what happened, saw the vehicle driving in the area beforehand or who may have captured any relevant dash cam footage.”
Anyone with information is asked to email [email protected] or call 101 quoting Operation Gulf.