MONTREAL -- Quebec's anti-corruption squad announced Friday it is dropping a long-standing investigation into alleged bribes involving fundraisers for the Quebec Liberal Party.

Projet Justesse was an investigation that started in 2010 to look into into allegations that three party fundraisers - William Bartlett, Franco Fava and Charles Rondeau - as well as Marc-Andre Fortier, then-president of the Societe Immobiliere du Quebec, were involved in a kickback scheme involving transactions undertaken by the now-defunct government real-estate corporation.

On Friday, UPAC chief Frederick Gaudreau announced that the investigation was being dropped, saying in a statement that UPAC does not believe it can succesfully make a request with Quebec's Directeur des poursuites criminelles et penales to prosecute the suspects.

"The chief's decision was made objectively and in the interest of sound management," UPAC said in a statement, adding that it will not further comment in order to protect the confidentiality of police investigations.

Quebec Public Security Minister Genevieve Guilbault said she was surprised by UPAC's decision, and that it was not the denouement the government had been hoping for.

A spokesman for the Quebec Liberal Party said UPAC is an independent institution and that the decision to drop the investigation was made solely by Gaudreault. The party said it would have no further comment.

UPAC has come under fire in recent months over its failure to successfully charge and prosecute suspects in several high-profile cases.

In September, a judge stayed proceedings against Frank Zampino, former chairman of Montreal's executive committee, who was on trial for several corruption-related charges that stemmed from a UPAC investgation.