Question about P45/Leaving employment?

I got fired 29.01.2010 - been job centre etc, they require as well as new employers my p45 which im still waiting for. Lets just say me and my employer didn't leave on good terms. Im planning to write a letter in regards to my p45 and pay owed. Just wondered if anyone could tell is it his responsibility to get that to me or is it my responsibility to make sure i get it? As to be honest id rather not go back there as he has been very nasty and slandering my name with no evidence.