Mopsy --
Please DON'T write a policy! You can't change behavior with policy. Instead, take a look at the principles of a "healthy work environment" (yes, dear, look it up in the nursing literature!)
When a unit isn't working (as well as it could, or as well as it should) a good place to start is by examining your committment to relationship management -- relationships with each other (side-by-side and shift-to-shift) your relationships with management AND your relationships with the community you serve.
Taking responsibility for building positive and healthy work relationships can open the doors for LOTS of other successes.
You can find much about this concept in the surgical literature (AORN Journal) and probably in the ICU literature as well!
--p