There are two sides to George Clooney that are as bipolar as his famed salt-and-pepper hair. Although it would be fair to say that when he popped up in Venice to promote Michael Clayton, for which the former ER star is heavily tipped to be in Oscar contention, his hair was more salt than pepper. The salt of his public persona is the heightened interest that is taken in the private life of the famed bachelor. The pepper is his increasingly excellent turns in politically slanted movies that are set against ill-conceived wars and corporate monoliths. In Venice it seemed that he was after some extra gossip column inches as he chose the sandy beaches of the Lido to make public that he has a new squeeze.

On the 46-year-old’s arm was 28-year-old Sarah Larson. The hacks and paparazzi went into a frenzy to discover just who this girl was who had snared the movie world’s most eligible bachelor. The first information to surface was that the attractive brunette had once appeared on a TV show, NBC’s stunt competition show Fear Factor: Las Vegas, in which she partnered her then-beau Dan Randolph in an episode that aired in 2005. It didn’t take long for news to filter through that for the last three years she had been working at Vegas hot spots and met Clooney at the Ocean’s Thirteen premiere in June. This information didn’t come from the man himself, who responded to a question about his new girlfriend by asking: ‘When have I ever talked about my private life?’

Clooney has a way of saying everything with a smile. He deflects questions by flashing his white teeth that were the brunt of several gags in the Coen Brothers’ Intolerable Cruelty. Yet there is the old adage about many a true word being said in jest and responding to an innocuous questions about exactly who he thought his latest protagonist Michael Clayton was, Clooney responded: ‘You mean in the film? Oh I thought for a moment you meant me – who I am. I’m still trying to figure that out.’

There were smiles all round yet it didn’t hide the fact that Clooney is an Oscar winner who is bugged by the fact that more interest is taken in his private life than his performances on screen. At a press conference at the film festival in Venice, and later in Toronto, questions about acting and his craft were notable by their absence.

Clooney plays a jaded former criminal attorney in thriller Michael Clayton. At a New York corporate law firm, Clayton works as a fixer, the man called on to clean up embarrassing and major problems for important clients. He’s worked at the firm for 15 years and hasn’t made partner and never will, and now he’s burnt out and jaded. While he’s out resolving other people’s problems, his own personal life is a mess. His brother has left him with an $80,000 debt after a failed business venture and he doesn’t see nearly enough of his ten-year-old son. At the firm, tension is mounting as a huge settlement being organised by the firm’s chief counsel Karen Crowder (Tilda Swinton) is being threatened by the breakdown of the lead trial attorney Arthur Edens (Tom Wilkinson).

Clooney says of the part: ‘While Michael is great at solving other people’s problems, the film catches him at the apex of dissatisfaction with his career. He started out with ambitions of becoming a trial lawyer, but along the way what he really becomes is a bag man.’

The internal struggle of Clayton and the aesthetic of the film provided by first-time director Tony Gilroy (an acclaimed screenwriter) is very much a homage to the work in the 1970s of Alan J Pakula, Sidney Lumet and Sydney Pollack (a link given further substance by his supporting role in Michael Clayton). Clooney was excited by the prospect of making a movie in this spirit. He says: ‘The studios used to make Harold and Maude and Network and All the President’s Men. We want to try to use the things we learned from foreign films and from independent films in the 90s, and try to infuse them back into the studio system – which is how it used to be. It was a time of ground-breaking social progress, and filmmakers were really into reflecting that. This movie deals with social conscience in an entertaining way.’

Making films with a conscience has taken up a significant proportion of Clooney’s recent oeuvre. In addition to the anti-corporate ethos of Michael Clayton, Clooney made a stand against war in the Gulf in Syriana and Three Kings. Sandwiched between these was Good Night, and Good Luck. Clooney says that there has been a price to pay for taking on these challenging roles away from the output of Hollywood studios and that is that he has only been paid for two of the last eight movies that he has appeared in, presumably Ocean’s Twelve and Thirteen. He says, ‘The rest of the movies you do for as little as possible because you want to get the movies made. It’s not like you’re going to get rich off of The Good German, Good Night, and Good Luck or Syriana.’ Then in a return to goofy, smiley George he quips: ‘But it’s OK. I do all right. I’m fine.’

What he fails to mention is that he didn’t get paid because his level of pay was determined by how well the films did at the box office. The relative lack of success of the films has also seen the demise of Section 8, the company Clooney set up with Steven Soderbergh to make intelligent, thought-provoking films. Michael Clayton will be the last Section 8 film to feature Clooney. Reflecting on the end of the company, he says: ‘It became less about filmmaking and more about the things we didn’t want to do, like cutting trailers. We knew it wouldn’t be forever.’

Clooney is looking better than he has done for years. He turned up for his new film nearly a stone and a half over his usual weight after suffering from an injury that restricted his movement. Recent pictures of a slim line Clooney on a beach had tongues wagging that the star was ill. Asked about his dramatic physical transformation, he says: ‘I was playing American football with 20-year-olds everyday when making [the upcoming] Leatherheads. That is going to keep you fit.’ Yet when asked the same question on a TV interview a few days later he said: ‘I lost weight by cycling every day near my home in Lake Como, 18 miles straight up a hill,’ which sounds like a far more plausible explanation.

The only time Clooney seemed ruffled in Venice was during a press conference when an Italian journalist asked him how he could make coffee adverts for Nestlé when he made films that highlighted the corrupt practices of big corporations. The smile temporary slipped from his face as he retorted: ‘I’m not going to apologise to you for trying to make a living every once in a while. The truth is that I do an awful lot of work with people in boycotted countries, like in the Sudan, but I’m not going to try to reconcile my work here. I don’t really have an answer and that is sort of an irritating question.’ It is true that Clooney is one of the few actors who uses his fame to try to raise awareness of social ills. A few days after our interview, when Clooney was in France to pick up the Chevalier Des Artes et Lettres, he used the moment to once again highlight the current plight of citizens in Darfur.

Yet the actor always seems most at ease and happy when he can be a goofball and display his charm and wit. He is about to start work on the Coen Brothers’ latest film, Burn after Reading, alongside his good friend and Ocean’s co-star Brad Pitt. Clooney playfully jokes that Pitt is among a litany of celebrities famous for doing nothing and calls him ‘a tiny little man’ (ironic given that Clooney is far shorter than Pitt). Clooney the famed flatterer strikes again.

Michael Clayton is on general release from Fri 28 Sep.