DESPITE most separated couples agreeing that both parents should remain involved in their children's lives, about one quarter never talk to their ex-partner about matters relating to their children.

The finding emerged from a survey of 5000 parents commissioned by the Howard government.

Almost 80% of parents surveyed agreed that continuing involvement of both parents would be beneficial, but for many the relationship with their ex-partner had deteriorated.

One quarter of separated fathers and mothers described their relationship as distant. Almost 20% reported lots of conflict, while 11% of mothers and 2% of fathers characterised their relationship with their former partner as fearful.

The survey was conducted in 2006, but the results have just been released by the Australian Institute of Family Studies.

One of the authors of the report, AIFS researcher Lixia Qu, said the evidence indicated that an acrimonious relationship between parents could be to the children's detriment.

"When parents separate, anger can get in the way and they suddenly lose sight of the children," she said.

This can also flow on to the relationship children have with their grandparents, particularly when children have a close bond with the parents of their own non-residential parent.

A spokeswoman for Families Minister Jenny Macklin said the best interests of children were at the centre of the Government's family policies.

"We need to support parents to build workable relationships so that family networks are maintained even though they are in a different form," Ms Macklin said.