Competition Commissioner John Pecman called their alleged actions "egregious anti-competitive behavior that harms Canadian consumers" and "a serious criminal offense."
A whistleblower triggered the investigation that uncovered "evidence suggesting that the accused conspired, agreed or arranged to fix prices of chocolate products," the Competition Bureau said in a statement.
Three individuals were also charged: Robert Leonidas, former president of Nestle Canada; Sandra Martinez, former president of Confectionery for Nestle Canada; and David Glenn Stevens, head of Canadian food distributor ITWAL.
The indictments follow similar charges against chocolate sellers in Germany, including Nestle and Mars, that resulted in multimillion dollar fines last January.
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Canadian officials said Hershey Canada Inc., an alleged co-conspirator, cooperated with the anti-trust investigation and agreed to plead guilty at a hearing on June 21 in exchange for leniency.
A fifth unnamed company that claimed to be part of the cartel revealed the scheme as part of a program offering immunity to whistleblowers who disclose an offense not yet detected or provide evidence leading to charges, Pierre Yves Guay, a spokesman for the Competition Bureau, told AFP.
"It's difficult, however, to estimate the amount of the overcharging because of the complexity of the pricing in that market," he said.
How the scheme worked is expected to be revealed at Hershey's trial in Toronto.
Hershey said it would plead guilty in Ontario Superior Court to one count of price fixing "related to communications with competitors in Canada in 2007."
The company said it had "promptly reported" the alleged scheme to the Competition Bureau at that time and insists it "did not implement the planned price increase that was the subject of the 2007 communications."