Montreal's Auditor General says corruption in City Hall was a "perfect storm" of forces conspiring to rip off taxpayers.

Jacques Bergeron told the Charbonneau Commission on Tuesday that colluding businesses teamed up with corrupt white collar workers to create a seamless system designed to hide in plain sight.

He said that because senior employees were corrupt they were able to hide or falsify documents as needed to evade detection.

Bergeron, whose investigations led in 2009 to the largest contract in the city's history being torn up because of collusion, said the most astounding part of his work was how not a single employee ever complained to any authority about what was going on.

"It's very surprising there were no accusations from people who may have observed these kinds of situations, evidently most likely because of fear of retaliation. People probably saw things, but didn't want to talk about them," said Bergeron.

The corruption inquiry is no longer looking for instances of collusion but is now in its recommendation phase.

Bergeron said there must be honest employees at City Hall, but that they were likely afraid of losing their job -- or worse -- if they spoke up, and so he recommends iron-clad protection for whistleblowers so they will be able to come forward.

He also said a system should be in place so employees can speak to someone beside their superiors about irregularities.

Bergeron said that managers and employees also need to be trained on how to spot collusion and price fixing.