The amount of time Hollywood will devote to laughing at itself during Sunday's Oscar ceremony was dramatically reduced yesterday when a sketch starring Sacha Baron Cohen was pulled from the line-up in order to protect the feelings of James Cameron.

Organisers confirmed that the British comedian would no longer be appearing on Hollywood's biggest stage following reports that the show's producer, Bill Mechanic, had refused to green-light his near-the-knuckle satire of Cameron's science-fiction blockbuster Avatar.

The proposed sketch, which Baron Cohen was hired to co-write and perform with Ben Stiller, would have seen the man behind Borat, Bruno and Ali-G play a female member of the Na'vi, the tribe of blue-skinned aliens at the centre of Cameron's Oscar-nominated film.

Unconfirmed (but so far un-denied) reports suggest that the skit was to culminate in Baron Cohen's character revealing that she was pregnant with Cameron's love-child, before walking into the audience to confront the director in the style of a guest on Jerry Springer's TV chat-show.

Mr Mechanic has yet to comment on what exactly persuaded him to axe it at such short notice. But he ran the Hollywood studio which collaborated with Cameron on Titanic, meaning that he is well aware of the filmmaker's reputation for occasional prickliness.

A near-the-knuckle skit would also have risked falling flat during the live performance. And if either Cameron, or the tens of millions of American families watching on live television were to take exception to its contents, their complaints might have overshadowed the entire event.

A spokesman for the Academy, which had included Baron Cohen and Stiller on a list of its celebrity performers published only last week, confirmed that the British star would no longer be appearing on Sunday, but declined to offer an on-the-record explanation as to why.

Matt Labov, a Hollywood publicist who represents Baron Cohen, was more forthcoming: "I hate to use the term, because it's so ubiquitous, but there were 'creative differences'," he told New York magazine, which broke news of the affair.

"Nothing acrimonious, but both sides felt that since they couldn't agree, [Cohen] might as well remain in London."

Baron Cohen isn't the only victim of painstaking attempts by Oscar organisers to steer clear of anything that threatens to cause controversy.

On Tuesday, it was confirmed that Nicholas Chartier, a producer of The Hurt Locker, a narrow odds-on favourite to beat Avatar to the Best Picture gong, had been banned from the awards show for breaking strict rules governing campaigning.

In an email to voting members of the Academy last month, Mr Chartier had urged supporters of independent film to back his title "and not a $500m film" like Avatar.