Doctors at East Lancashire Hospitals NHS Trust are asking people to stay away from A&E, unless they have a serious or life-threatening condition.
The trust, which includes Royal Blackburn and Burnley General hospitals, had 148 people waiting for emergency care at one point on Wednesday.
It has posted a series of pleas online urging those seeking urgent care to consider whether a hospital is the best place for that, or whether they should contact NHS 111 for other options.
Medics have asked patients to understand that, despite what are described as "very long" waiting times, they are doing their best to see everyone "quickly."
Chief Operating Officer, Sharon Gilligan, added that they want people to "take every effort" to protect themselves including getting vaccinated, maintaining good hand hygiene and social distancing.