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:
Offaly Farmer Loses Faith In Government After Masked Raid
OPW Sites Offering Free Admission For Under 18's Next Month
Focus Ireland Highlights Impact Of Child Homelessness
Tate Extradition Case Sends “Message Of Hope” To Survivors - Domestic Abuse Charity
Laois TD Calls For More Budget Support For Middle-Income Families
Midlands Car Insurance Costs Revealed
Truck Overturns On Laois Motorway
Man Left Hospitalised After Workplace Incident In Westmeath