The Montreal archdiocese has called on a retired judge to conduct an audit of sexual abuse claims levelled at the church over a span of nearly seven decades.

Five Montreal-area dioceses will be taking part in the review to be led by former Superior Court justice Anne-Marie Trahan, the organizations announced Wednesday.

Montreal Archbishop Christian Lepine said Trahan will have unfettered access to all documents -- general archival documents as well as reserved archives typically only viewed with the archbishop's approval.

"The aim is to look for the truth, whatever it is, wherever it leads us," Lepine said in an interview Wednesday.

Trahan's mandate is to look at the "number and the nature of well-founded allegations of sexual abuse of minors made against Catholic clergy and mandated lay personnel from 1950 to the present," the archdiocese said.

She accepted the role after being assured she would have access to the required files covering the nearly 70-year period, and that the findings would be published.

The audit, which is expected to begin in September, is an important first step, said Lepine, who has been archbishop since 2012.

"It's the right moment to do it -- it's about many things, but it's also about listening to the victims and we need to see what is our track record about listening to the victims from 1950 until today, and we need to be truthful about our history," Lepine said.

The review, which will focus on people working in parishes, services and institutions in the five dioceses, doesn't have a set time limit. Lepine said Trahan has told him she expects it could take up to two years.

Lepine acknowledged the conclusions could be difficult to hear if the extent of abuse is worse than expected.

"Looking at your wounds or weaknesses or you sins is not easy, but it's something we need to do," he said. "Pope Francis said at one point we need to find the truth, wherever it leads us, because it's the only way we're going to speak with credibility about the love of God."