Quote from LadyFree28
Even if you are interviewing for another company, your previous company can only VERIFY that you worked there, regardless of what your boss thinks ...
(Again, as already noted, this isn't true
-- a lot of companies have a policy
of only verifying hire/separation dates, but there is nothing legally preventing employers from providing more information, and giving people bad references as long as the information is factual.)
OP, employment applications often (usually?) ask for professional references in addition to a list of previous employers, and it is entirely appropriate to use your previous managers as references (after checking with them that they are willing
to be references for you).