The incident happened just before 6 a.m. in Newchurch Road, near the junction with New Line. A Vauxhall Vectra was travelling east and was involved in a collision with a cyclist.
The cyclist, a 52 year old woman from Bacup, was taken to the Royal Blackburn Hospital with serious head injuries and has since been transferred to the Royal Preston Hospital and she remains in a serious condition. The driver of the car, a 75-year-old man, also from Bacup, was not injured.
Accident Investigators attended the scene and the road remained closed for three hours while they carried out their work.
Senior Investigating Officer Patrick Worden from the Road Policing Unit, said: “I would appeal to anyone who was in the area at the time and who may have witnessed the incident to come forward and contact police.
“The female cyclist remains in a poorly condition in hospital and her family have been informed.”
Anyone with any information is asked to call Lancashire police on 0845 1 25 35 45.