At around 9.45am on Saturday, emergency services were called to the East Lancs Road at the junction with Houghtons Lane, following reports of a collision between a Peugeot 206 and an Audi Q7 on the Liverpool-bound carriageway.
The driver of the Peugeot, a man in his 50s, was taken to hospital with and found to have suffered a serious head injury. His current condition is critical. The driver of the Audi was uninjured and is assisting with enquiries.
CCTV and witness enquiries are ongoing and anyone with information is asked to contact our Roads Policing Unit.
Roads Policing Sergeant Ryan Lowry said: "As this investigation continues, we need to hear from any witnesses who are yet to come forward. Yesterday was an extremely busy day on our roads so I would appeal to anyone who was travelling on the East Lancs near to Houghtons Lane around 9.45am to let us know.
“We also need to find and speak to the male driver of an HGV who stopped at the scene but did not leave contact details. I would also ask that anyone in the area please checks their vehicle dashcams too as what could appear insignificant to you could be vital to our ongoing investigation."
Anyone with info is urged to call the Roads Policing Unit on 0151 777 3339, message our social media desk @MerPolCC, or call 101 quoting reference number 354 of 22 December.