Officers say the incident happened at the Capitol Centre on Wednesday evening after a woman allegedly entered a shop, selected various items and attempted to leave without making payment.
A staff member attempted to stop the woman who then allegedly kicked him in the stomach and threatened to stab him with the hypodermic needle before making off in the direction of Yew Tree, London Way.
Police say this is the latest in a number of thefts which have taken place over recent weeks with Next and Capitol Centre, Walton Le Dale.
A spokesman for the police said: "We appreciate that the quality of the still images are poor, however we are confident that somebody will be able to recognise her.
"If you recognise her and/or have any information please contact Preston Police."
Anyone with information is asked to contact police on 101 quoting log reference number LC-20180509-1162.