The call follows widespread concern over the small number of rape convictions compared to a rising number of detected rape and sexual assault cases.
Figures released by the Department of Justice in July show that sexual offences increased by 886 to 1,956 last year an 83% increase on the year before.
But according to the Dublin Rape Crisis Centre's Sexual Abuse and Violence in Ireland (SAVI) report, published this summer, only about 3% of reported rapes ever result in a conviction. The SAVI report showed that last year just 31% rape victims reported their rape and of those who did just 9% resulted in convictions.
Campaigners say the fact that the DPP does not give reasons for dropping a case leaves many women feeling guilty and does nothing to encourage rape victims to come forward.
"They really feel that when their case is not pursued by the DPP that someone is blaming them. It feels like a judgement," said Geraldine Connelly, head of clinical services at the Dublin Rape Crisis Centre.
"If at the end for some reason unknown to you, your case is dropped, it just adds to the trauma and you have no result," said Ingred Wallace of Rape Crisis Network Ireland (RCNI).
Kate Mulkerrins, barrister and law tutor at NUI Galway, said it was important for the DPP to explain why cases are dropped to expose the inadequacies of the law regarding rape.
"You legally cannot convict someone if they defend themselves on the basis that they thought consent was given," she said, adding that unless there was obvious brutality or violence the consent argument was a ready-made defence for rapists.
If the DPP began telling victims that cases could not be taken because the law made it nearly impossible to win if a case is contested, the law would have to change, Ms Mulkerrins said.
"I don't think anything is going to change quickly unless we have a degree of public outrage about this ," she said.
The issue is one of the legal issues surrounding sexual abuse to be discussed at a conference this weekend in Galway which will hear from several academic experts including Ms Mulkerrins. Other issues will include the up to two year delay experienced by victims waiting for rape trials.
A spokesperson for the DPP last night declined to comment. However, the director has previously indicated that if he gave a reason in one case he would be expected to do so in all cases. This view was upheld by a Supreme Court ruling in 1994.
* The Rape Crisis Network Ireland can be contacted on 091-563676 for details of this weekend's conference.