Top judge says children are used in battles of separation.
Speaking at a conference at Ansty, near Coventry, Sir Nicholas Wall said separating parents "rarely behave reasonably" and a less adversarial system was needed in the family justice system.
Separation was, he said, "of itself, a serious failure of parenting".
In a speech to the Families Need Fathers charity, the judge, who is president of the Family Division, said: "Separating parents rarely behave reasonably, although they always believe that they are doing so, and that the other party is behaving unreasonably.
"People think that postseparation parenting is easy - in fact, it is exceedingly difficult, and as a rule of thumb my experience is that the more intelligent the parent, the more intractable the dispute."
Sir Nicholas said family law does not easily fit into the concept of an adversarial system where "something is nearly always somebody's fault".
"Many parents make matters worse by their disputes over their children. They forget the loyalty children have to each party," he said.
"These problems are best resolved outside the courtroom, not in it.
"Disputes over contact between absent parents and their former partners are rarely about the children concerned. Far more often, the parties are fighting over again the battles of the relationship.''