Smear tactics, negative adverts, character assassinations -- these are terms normally associated with presidential campaigns, not Hollywood's most prestigious awards bash.

But when it comes to the Academy Awards, which takes place next Sunday, Tinseltown's major movie studios will often resort to any means necessary to bag an Oscar for one of their films or stars, even if it means resorting to underhanded methods to trash their rivals.

Slumdog Millionaire, the overwhelming favourite to win the Best Picture prize next weekend, would appear to be the main target this year. Earlier this month, stories emerged accusing producers of exploiting and underpaying the two Indian child actors used in the movie.

The film's director, Danny Boyle, and producer, Christian Colson, have since been frantically engaging in damage limitation, emphasising that the two kids, Rubina Ali and Azharuddin Ismail, were paid three times the average local adult salary for 30 days' work, as well as being enrolled in school and set up with fund accounts that they will receive until they turn 18.

Nobody can say for sure that the cheap labour story was deliberately designed by a rival studio in order to derail Slumdog's chances, but, as Los Angeles Times film critic Pete Hammond pointed out, it is surely more than coincidental that the negative reports broke in the press on the same day as the Oscar ballots were mailed out to Academy voters.

An Oscar win can dramatically transform an actor's creative and earning power, and movies that make the frame at Oscar time can rake in as much as $100m extra at the box office. For those reasons, mud- slinging and muck-raking have long been a feature of the annual Academy Awards race.

Indeed, an effective smear campaign is believed to have denied the Best Film award to Orson Welles' Citizen Kane (1941), which has regularly been named by critics as the greatest movie ever made.

The title character in Welles' movie, Charles Foster Kane, was a thinly-disguised version of real life newspaper magnate William Randolph Hearst, then owner of over two dozen tabloid publications across the US.

Hearst took personal offence to the depiction in the movie and so banned reviews and mentions of the movie in his papers (except to trash Welles personally), as well as limiting its run in cinemas, hence ruining its potential at the box office.

Kane still received nine Oscar nominations, but Hearst had done so much to bad-mouth the movie that boos were reportedly heard in the audience every time the film's name was mentioned at the 1942 ceremony. The film took home one award for Best Screenplay but lost the Best Picture and Director prizes to How Green Was My Valley.

Similarly in 1952, the critically praised western High Noon, starring Gary Cooper and Grace Kelly, became the focus of a whispering campaign by rival studios that suggested it was pushing a liberal agenda and making "un-American" statements on both US involvement in Korea, and the notorious Hollywood anti-Communist blacklist. As a result, High Noon lost the Best Picture award to Cecil B De Mille's ridiculous circus movie The Greatest Show on Earth.

However, the past 15 years have seen some of the nastiest Oscar races ever, as rival studios upped their spending on campaigns to as much as $20m per movie and the rise of the internet ensured that damaging gossip and innuendo could fly around the world before the truth had even got its boots on.

For example, in 1998 20-something newcomers Matt Damon and Ben Affleck were nominated for Oscars for writing the screenplay for the hit movie Good Will Hunting. It was the kind of success story that Hollywood loves, but that wasn't enough to stop a fervent rumour campaign that suggested the two guys hadn't written the script at all, but that it was actually penned by legendary screenwriter William Goldman. Damon and Affleck strenuously fought the charges, saying they had shown their original script to Goldman and that he had suggested chopping one subplot from the story, which they did. Goldman himself issued a statement to that effect, and Damon and Affleck ended up taking home the gong for Best Original Screenplay.

The 2001 Oscar race plumbed even lower depths than that. Veteran star Sissy Spacek entered the award season as the favourite to win Best Actress for the indie drama In the Bedroom.

That was until an anti-tobacco lobby group placed full page ads in the New York Times accusing the film of promoting smoking by featuring several scenes of Spacek and her co-star Marisa Tomei puffing on cigarettes.

The film's producers Miramax accused rivals of trying to smear the movie in the minds of health-conscious Californian Oscar voters and vigorously fought any charges of product placement.

The movie won nothing from five nominations, with Spacek losing to Halle Berry in Monster's Ball.

The frontrunner in 2001 was Ron Howard's A Beautiful Mind, a biopic of schizophrenic Nobel Prize-winning scientist John Nash, played in the movie by Russell Crowe. Competitors first put the film under fire for omitting significant details from Nash's life, notably that he was bisexual and that he abandoned his first wife (played in the movie by Jennifer Connelly).

Worse was to come. Four days before voting closed, another story emerged on the Drudge Report website (which broke the Monica Lewinsky scandal) accusing Nash -- who was still alive at the time-- of being an anti-Semite, pointing to a statement he released in 1967, at the height of his illness it must be said, calling Jews "the root of all evil as far as my personal life is concerned".

Nash himself then had to take part in a prime-time television interview to address the charges and defend his reputation. Suspicion about the motivations for the character attacks was fuelled further when an "Oscar strategist" with a rival studio called the LA Times to alert a reporter to the anti-Semitism story on the Drudge site. Despite all the negativity, A Beautiful Mind won four Oscars, including Best Film.

The following year, dirty tricks were everywhere yet again. Rumours started doing the rounds in the weeks before the ceremony that Best Actress nominee Nicole Kidman had had an affair with married actor Jude Law during the filming of the movie Cold Mountain.

The Aussie beauty's lawyers declared war on any publication that carried the baseless rumour, and even Cold Mountain director, the late Anthony Minghella, felt compelled to issue a statement denying any affair between the two actors. Kidman went on to win the award for The Hours. Even more controversial that year was the nomination for director Roman Polanski for Holocaust drama The Pianist.

The Czech-born filmmaker has lived in exile from the US since 1978, having fled to Europe following his arrest for the statutory rape of a 13-year-old girl named Samantha Geimer.

Amidst a heated debate about Polanski's contentious nomination, Geimer herself wrote a peculiar article in the LA Times saying Oscar voters should "vote for the movies they feel deserve it".

She followed this up with an appearance on Larry King saying she had forgiven the director for what he had done to her.

Many questioned the timing of Geimer's intervention, accusing The Pianist's backers, Focus Films, of using the woman to help Polanski's chances.

Then, in a move seen as a fight-back by a rival studio to impugn Polanski all over again, court transcripts that graphically detailed just what Polanski did to Geimer turned up online.

In any event, Polanski went on to win the Oscar for the movie, which also won two other major gongs on the night, perhaps proving once and for all that, when it comes to the Oscars, bad publicity is often better than no publicity at all.

By that measure, Slumdog could well be top dog this year after all.