The family of Sophie Toscan du Plantier has appealed to the Government to maintain co-operation with a French magistrate who is investigating the film producer's death in West Cork in 1996.
Her family said they are being denied justice by the failure to resolve the murder more than 17 years after it occurred.
Ms Du Plantier's parents, Marguerite and Georges, both aged in their 80s and in poor health, did not travel to Ireland.
Their feelings were relayed to a news conference by the association campaigning for the truth about their daughter's murder.
The association said it and Sophie's family are frustrated and disappointed that there have been what they describe as "obstructions" placed in the way of resolving her murder.
An investigation is taking place under a French Judge, Patric Gachon, and a team of French detectives is due to return to Cork to take statements from witnesses on Monday.
The association is appealing for Irish co-operation with the French investigation to continue.