The man in his 80s was hit by the Ford Transit, which failed to stop, in Marine Parade West yesterday afternoon.
He was hospitalised following the incident, and police are appealing to the public to ascertain what happened.
A statement from Hampshire Constabulary said: ‘We are appealing for witnesses after a man suffered life-threatening injuries in a collision in Lee-on-the-Solent yesterday afternoon.
‘Police were called just after 2pm, following a collision involving a pedestrian and a Ford Transit van on Marine Parade West.
‘The pedestrian, a man in his 80s, has suffered severe injuries and has been taken to hospital, where he remains.’
After initial enquiries by officers, the vehicle was found in Curdridge.
Police have arrested a 48-year-old man from Gosport in connection to the collision.
He was detained on suspicion of being in charge of a motor vehicle while alcohol level above limit, failing to stop, causing serious injury by dangerous driving, driving whilst unfit through drink and driving whilst unfit through drugs
The man is in police custody.
‘While we have heard from a number of people who have had information which has assisted our enquiries so far, officers remain keen to speak with anyone who can assist’, Hampshire police said.
‘We are particularly keen to hear from anyone with dash cam footage of the collision, or the moments just before or after.
‘Anyone with information should call 101, quoting the reference 44220254443.’