MONTREAL -- The man who infiltrated the New York Mafia and inspired the movie "Donnie Brasco" is describing how he saw the underworld take over the construction businesses using methods that would be familiar to Quebecers today.

Joseph Pistone, a legendary FBI agent who spent six years undercover as a Mafia associate starting in the late 1970s, told the Charbonneau Commission about the inner workings of the Mob in the United States during his testimony on Monday.

He described its control over labour unions and businesses that owned raw construction materials -- so it consistently managed to claim a piece of the profit, even for public contracts where a Mob-linked company wasn't ostensibly involved.

In one example he cited, Mafia-run construction companies would claim to hire more expensive unionized labour while actually paying cheaper non-union rates.

He cited different reasons for why the Mafia would have been allowed to become so powerful. First of all, he said businesses are making a grievous error when they allow themselves to get extorted by the Mob -- because it will keep coming back for more.

He also lamented that the general public has romantic notions about the Cosa Nostra, thanks to Hollywood-fuelled images of men with colourful vocabularies wearing $5,000 suits.

"Believe me -- they don't quote Shakespeare," Pistone said. "This is not the movies... They are a dangerous plague on our society."

"The public has an image of an honourable society. The Mafia is not honourable," he said. "Legitimate businessmen, when they are approached tby the Mafia, should report it to law enforcement.

"Once you give in... they never stop... It's not just one time."

He said Mob scams ultimately get passed on to taxpayers and consumers, in the form of higher prices. He said governments and police forces have a responsibility to never lose sight of the threat it poses, and to keep fighting.

Quebec's commission is looking into criminal corruption in the construction industry and its ties to organized crime and political parties.

The corruption scandals in the province blew wide open three years ago, with media reports of a construction cartel called the "Fabulous 14" that allegedly colluded on bids for public-works projects. Pistone described a similar system in the U.S.

In his morning testimony Monday, he told colourful tales about how he infiltrated the Mob while pretending to be a jewel thief.

He also discussed the ways of the underworld, including its moral codes and its list of offences that would get people killed.

His early testimony had been a mish-mash -- or, as he calls it, a "mix-mash" -- of anecdotes from the Mafia life he observed three decades ago, laced with street-wise lingo.

In one example he described taking a slap from a so-called "made" man and thinking that, under ordinary circumstances, he would have punched the guy; he had to refrain, because full Mafia members were untouchable.

What Pistone has not done, so far, is delve into the workings of the Canadian Mafia.

He had just begun discussing ties between the New York families and their Canadian counterparts when the testimony broke for lunch. Pistone referred to a killing of Mafia capos committed by a hit squad that included Montreal's Vito Rizzuto, although he did not mention Rizzuto by name.

When he came back in the afternoon, he discussed the construction industry.

Pistone, now 73, is testifying under heavy security at the inquiry behind a screen.

Commission chair France Charbonneau has imposed a ban on the broadcasting or publication of any image of Pistone from Monday's hearing. The ban does not extend to photos or footage taken in the past.

His testimony has focused so far on the six years that he spent undercover running with the Bonanno crime family in New York City, an unprecedented police operation that saw law enforcement get as close as it ever has to the Mafia.

Much of his testimony has been the subject of books Pistone himself has already written, as well as the 1997 Hollywood blockbuster "Donnie Brasco."

He was pulled from the operation just as he was about to become a made man, Pistone said, with his bosses making the call to pull him out. He said he was disappointed to see the operation suspended.

"No one had ever gotten this close to a Mafia family," Pistone said.

"My argument that was we're going to embarrass them by having an undercover with them for all these years, can you imagine if it comes out they inducted an FBI agent?"

Pistone's undercover work led to some 20 trials and 200 convictions across the U.S. But the Bonanno clan continues to exist to this day, Pistone says, and still has strong ties to groups in Montreal as it did when he was embedded.

Pistone's testimony at the Charbonneau commission is intended to help the inquiry better understand the murky world of the Mafia as a whole.

Other witnesses testified last week about how Mafia families function.

Honour and loyalty are key, Pistone said. Orders to underlings are to be carried out without question -- even when the order is to kill someone. There is no debating or discussing such things, he said.

"Your sworn allegiance is to your Mafia family: it's your Mafia family, then your regular family, then your church and country," Pistone said.

"But your first allegiance is to that family that you're a part of."

Pistone, who assumed the Brasco identity during his undercover days in the mid-1970s and early 1980s, is still hiding from the Mafia as a result of his old career.