Independent TD Finian McGrath was rebuked by the chair of the Oireachtas Justice committee after asking questions about the circumstances in which the popular priest died and the garda investigation into his killing.
But chairman David Stanton ruled the questions out of order, saying the committee had agreed not to raise the matter while the meeting was in public session.
Fr Molloy (52) was murdered at the home of his friends Richard and Therese Flynn in Co Offaly in July 1985 after requesting the return of a large sum of money owed to him.
The murder took place after a wedding party attended by several politicians.
The priest was beaten up and his battered body placed in the bedroom of the Clara mansion.
His death has been raised in the Seanad in recent weeks by Senator John Whelan, with allegations that his death was covered up.
Gardai have denied this, saying there was no evidence of a conspiracy, but there have been calls for an independent inquiry.
In a separate development, Garda Commission Martin Callinan told the committee there was some 25 organised crime gangs in the State, with most operating in Dublin, Cork, Galway, Sligo, Limerick and Cork.
The gangs often conspired to import large quantities of drugs, and worked with dissident republicans.
Deputy McGrath asked how Gardaí were tackling the issue of young people “being sucked into gangs”.
Commission Callinan said that many teenagers associated crime with providing a “different lifestyle”, and that Gardai were working with communities to get the message through that crime did not pay.
But he admitted gardai “didn’t get through to everyone”.