A decision by the United Nations' Security Council (UNSC) last week to investigate the allegations has been welcomed by Alliance Defending Freedom (ADF) - a Christian group which speaks out against persecution - as a "really important first step".
But senior policy officer, Ryan Day also told Premier: "It has taken too long. We are just at the point now - years down the line - of court-ready evidence being collected or International Criminal Court category crimes; crimes against humanity and genocide."
The UNSC voted unanimously on Friday to establish an investigative team led by a special advisor to work with the Iraqi government in assessing the treatment of groups including Christians and Yazidis at the hands of IS.
Where necessary, the group will collect evidence of crimes committed by the terror group. Friday's resolution marks the first time the UNSC has used the term genocide in reference to Islamic State's actions.
Expressing hope that the investigation will hear local voices, Mr Day added: "Our prayer at ADF is that the investigation that is to come really engages with high-level advisors in the academic field and non-governmental organisations on the ground".
It is expected a special advisor to head the investigation will be appointed by UN Secretary General António Guterres within the next couple of months.
Click here to listen to Premier's Alex Williams speaking Ryan Day from ADF: