What are my legal options? Libel, Slander? How do I proceed?

A co-worker has been engaging in phone conversations and email with my supervisor and manager. I have overheard him on a couple of occasions and I have seen an email. The contents are full of false statements aimed at me and another co-worker. The co-worker making the statements was previously my supervisor but has been remover from his acting position due to his inappropriate actions with staff. A mediator was brought in to deal with the office. He(the co-worker) was removed from his supervisor role following the mediation. I live in Yukon Canada. I feel my career might be compromised because of his false statements to my manager. What legal option do I have?