A Volkswagen Tiguan left the road before overturning as it was travelling south along Moss Lane at around 12.30pm on Monday (October 11).
The driver of the car, a 19-year-old man from Southport, suffered serious head and internal injuries.
He was taken to Aintree Hospital before being transferred to the Walton Centre for further treatment.
Sgt Chris Evans, of Lancashire Police, said: "An investigation is underway following a road traffic collision in Burscough which has left a man seriously injured.
"We are appealing for information and very keen to speak to any witnesses, or anyone with dashcam footage which shows what happened.
"If you can help please come forward and call 101, or email [email protected] quoting log 0648 of October 11."
Any information can also be reported online at doitonline.lancashire.police.uk.
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