Any lawyers about? Defamation of character

Is it possible to sue and/or censor an individual who makes wild and untruthful accusations about another individual?

Scenario:

Person A (he) was married to Person B (she) and had one child with her - person C (who is now about 25yo, male).

Person A and person B got divorced a long time ago and person C stayed with the mother (person B).

8 years ago, person A married a new person (person Z) and they are still happily married.

Now it transpires that person C (the son) has been having 'emotional problems' and has been abusing his partner. Person C blames his upbringing and person A (father) for his abusive ways.

Person C has been sending nasty and vindictive e-mails to his father (person A). in addition, person B (ex-wife) been sending lies not only to Person A, but to Person Z (current wife) in an attept to damage their marriage (A and Z).

in particular, Person C (son) has been telling Person Z (current wife) that Person A (his father) used to physically abuse Person B (his mother; person A's ex-wife).

This is not true. Can anything be done without a large legal expense?