By Emma Jones
BBC News reporter in Venice
Damon had to pile on the pounds for his latest role
The serious issue of corporate greed has been dealt with by Hollywood before - most notably with The Insider. But in The Informant, director Steven Soderbergh and Matt Damon play it for laughs.
Soderbergh has turned the real life story of Mark Whitacre - the biggest ever whistleblower in US company history - into a black comedy.
"Steven and I were just saying over lunch, 'thank God we did that'," recalls Damon, "otherwise it would be basically a movie mirroring exactly what we're seeing on TV right now from corporate America."
Damon and Soderbergh are in Venice for the world premiere of the movie, which has been seven years in development.
It has been screened on the same day as Michael Moore's Capitalism: A Love Story and Oliver Stone's South of the Border - which also deal with financial greed.
"It's much easier to get your point across in a movie rather than a soapbox," says Damon.
"It does reflect the current times, but still, we found Mark Whitacre intriguing and fascinating long before any of this stuff about economics and the downturn became headlines. We'd finished shooting the movie before it actually happened."
Damon's toupee caused an amusing moment
Mark Whitacre was a divisional president of food company Archer Daniels Midland (ADM) until 1995, when it became known that he had been acting as an informant for the FBI over price-fixing.
During the investigation, it was found that he had been embezzling millions of dollars from ADM and was jailed for nine years.
In the movie version, Whitacre's lies are exposed in quick and often hilarious succession, leaving the audience to decide whether he is a hero or villain.
"The energy it takes to lie like that is a full-time job," admits Damon.
"The interesting thing is, ADM was guilty of what he accused him of, but he was trying to protect himself by exposing their scam.
Some people still feel he was a good guy who was under a lot of pressure from the FBI, others that he had an existing bi-polar condition which should have been taken into account," he adds.
"What I don't understand is, as an attorney in the case asked at the start, 'Why is this guy doing this?' It's like everyone was blinded. If someone had thought seriously about it, it could have saved a lot of hassle."
Whitacre had an all-American appeal that gave him a certain celebrity when the scandal was exposed but Damon says his director summed up his appearance in one word - "doughy."
"Matt had to gain the weight in two months," Soderbergh says.
"I am not kidding, there's not a still photo taken off-set during the movie where he doesn't have a bag of chips in his hand."
Soderbergh met fans outside the Venice screening
"And I had a hairpiece, a moustache, cheek filler and a nose prosthetic," adds Damon.
Damon's toupee starts moving during one of the most serious moments of the movie - which was, inadvertently, the actor's idea.
"There was one moment during rehearsals when I scratched my head and the hairpiece moved. Steven screamed and said 'I have to use that in the film!'"
In the end, he used it in a really tragic bit, where the FBI is cutting him loose after all his lies have been exposed."
Soderbergh says the real-life Whitacre has seen the movie and approves of it. He is now a company director and still with his wife, who stuck by him all through the scandal.
"He's basically an optimist," explains the director.
"He said, 'Yeah, that's what it was like - I did some crazy stuff back then.'"
The Informant is released in the UK on 20th November 2009.