The chief counsel for the commission, Sonia Lebel, says the source of the error was an inverted licence plate number documented by the RCMP.
A firm owned by MNA Andre Villeneuve was among 74 mentioned by police, who took down the licence numbers of company cars parked outside the Cafe Consenza, a hangout for the Mafia that used to be located at a Montreal strip mall.
But Lebel said Thursday that Planchers Mirage Andre Villeneuve Inc., along with Construction LPG, should not have appeared on the list.
At the time, Villeneuve vigorously denied the link and defended his reputation. The PQ jumped to his defence when the link was suggested at the inquiry last September.
Villeneuve, 52, has represented the riding of Berthier since 2008.
The incident involving him comes with the inquiry facing additional scrutiny over the potential for unfair damage to reputations.
Recently, a key witness whose testimony was politically devastating to former Montreal mayor Gerald Tremblay, admitted he'd made up one of the stories he told.