If you can keep your communication businesslike, sticking to the facts and asking for clarification instead of making accusations, you are more likely to be able to start building a new way of relating to each other.

Remember, your son is learning from the two of you how to deal with conflict. Why not call the father and ask whether he noticed the bruises and whether he knows where your son might have got them?

Obviously, if there has been a history of domestic violence or, as you suggest, the father might have been using physical punishment, you two might want to discuss your concern and the safety of your child with a social worker, a parent coordinator or your lawyer.

From my clinical experience with high-conflict divorce parents, there are many motivational factors behind parental alienation.

Since you are able to ask before acting on your fears, you are considering what might be more harmful for your son's relationship with his father.

The best way to avoid being accused of alienating your child against his father is to become mindful of the nuances of what you say and do to avoid becoming a passive alienator.

As Dr Douglas Darnall points out in his book : "Telling your child something is your ex-spouse's fault is alienating. Instead, address the issue with the ex-spouse and do not put a child in the middle."

Consider honestly if what you are doing will foster a healthy, businesslike parenting relationship with the father. A paradigm shift is needed in divorce co-parenting. He is no longer your ex-husband, he is the father of your child. If he is being unpleasant, think of him as a difficult investor you need cooperation and funding from.

Hold your ground and integrity, be open to communicating your expectations and boundaries firmly but in a friendly manner. The more businesslike you can be, the easier it is to set up a way to communicate and rebuild a new form of family for your son.

Your son is the joint venture you are working on with his father. Both of you want your son to reach his full potential. If the prospect for developing a new way to communicate seems iffy, bring in a professional trained in coordinating parenting. It can prevent your exchanges from spiralling into a high-conflict relationship. You cannot change the father of your son, but you can change your attitude and be part of the solution in building two new families for your son.

Lora Lee is a registered psychologist and parenting counsellor working in private practice as an adjunct to her work at St John's Counselling