Maurice McCabe says he no longer wants an inquiry into his whistleblowing allegations to take place in private.

Sergeant McCabe issued a statement this evening, saying he's endured "eight years of suffering, defamation and state vilification" as a result of his actions.

He outlines the many inquiries that have already taken place in private into his allegations, and says he does not want to wait months while a "secret investigation" takes place behind closed doors.

Sergeant McCabe says it is imperative that any further inquiry into the matter take place in public.

Sergeant McCabe adds that he does not believe Commissioner Noirín O'Sullivan's denials of involvement in discrediting him.

Earlier, Commissioner O'Sullivan said "I am innocent" in a statement on the alleged smear campaign.

Opposition parties have expressed support for their Sergeant McCabe's call for a public inquiry.

Sinn Féin Deputy Leader Mary Lou McDonald says a Commission of Investigation is no longer viable: