Two men - one armed with a baseball bat and one with a knife - approached the rear of an address in Hall Lane and confronted the occupant, who was outside at the time, at around 8.10pm on Saturday (October 24).
The occupant, a man aged in his 50s, ran into the house but the burglars pushed past him.
Once inside the property they threatened the man's partner at knifepoint and stole a small amount of cash and mobile phones.
Before they fled the scene one of the men hit the victim on the arm with the baseball bat, but police have confirmed his injury is not serious. The knife has since been recovered.
Officers are now appealing for anybody with information to come forward, and are especially keen to hear from anybody with dashcam or CCTV footage taken in the area between 7.30pm and 8.30pm that night.
DC Dawn Croucher, of Ormskirk CID, said: "This was an incredibly traumatic incident for the couple and it goes without saying that nobody should be made to feel that terrified in their own home.
"We are in the very early stages of an investigation but we are determined to find the people responsible and we are now asking anybody with information that could help our enquiries to get in touch with us as soon as possible.
"Perhaps you know who may be responsible. Maybe you have dashcam or CCTV taken in the area at around the time of the incident. Or perhaps you have been in the Hall Lane area, close to Wrightington Hospital and Appley Lane North, and have seen something suspicious.
"Whatever information you have, we would ask that you please share it with us straight away.”
Anybody with information has been urged to contact police by calling 101, quoting log number 1280 of October 24.
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