The party's internal procedure has been halted with gardaí taking up the case.
The Sinn Fein Leader is characterising the complaint made against Laois Offaly TD Brian Stanley, which has been passed on to gardaí, as "serious".
Mr Stanley has resigned from the party claiming he was unfairly treated by an inquiry into a complaint against him.
Mary Lou McDonald says the internal process has now been suspended - Deputy Stanley says the process was seriously flawed.
Speaking with Will Faulkner on Midlands Today, she says she couldn't outline the details of the complaint:
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