The force was called around 7.40pm yesterday to Southport Road near Hurlstone Hall following reports of an accident.
Police say a black Volkswagen Polo travelling eastbound was involved in a collision with a BMW car travelling towards Southport.
A nine-year-old boy, a passenger in the Polo, suffered serious head and neck injuries and was taken by air ambulance to Alder Hey Children’s Hospital for treatment. His condition is currently described as critical.
The driver of the BMW, a 32-year-old woman from Ormskirk, suffered a punctured lung, broken ribs, a broken elbow and broken forearm and was taken to Aintree Hospital for treatment.
The road was closed for four hours while accident investigators attended the scene.
Police are appealing for witnesses to come forward following the collision.
Sgt Pat Worden, from Lancashire Police’s Roads Policing Unit, said: “At 7.40pm on Thursday, August 18, a two vehicle collision occurred on the A570 Southport Road, close to Scarisbrick.
“The collision involved a black Volkswagen Polo and a black BMW 3 series that were travelling in opposite directions. A nine-year-old male passenger in the Polo received serious head and neck injuries and was airlifted from the scene to Alder Hey Children’s Hospital and is in a critical condition.
“A 32-year-old female driving the BMW suffered serious internal injuries and is being treated at Aintree Hospital.
“I am appealing to anyone who witnessed the collision that has not already come forward to make contact with us, particularly if you may have seen the black Volkswagen Polo travelling away from Southport at this time.
“Anyone with information can contact police on 101 quoting log reference 1323 of August 18.”