Renee Zellweger won best supporting actress in 2003

It is thought to be in response to a Dreamworks advert supporting House of Sand and Fog actress Shoreh Aghdashloo.

The advert included critics' cuttings saying Aghdashloo deserved to win in 2003, but the award would probably go to Renee Zellweger for Cold Mountain.

The next Oscars will be held in Los Angeles on 27 February, 2005.

Competing films

The House of Sand and Fog advert caused uproar. Dreamworks later apologised and took out an advert congratulating Zellweger on her Oscar win.

The new rule "prohibits specific and disparaging references to other pictures or individuals competing in a given category in ads, mailings, websites or other forms of campaign communication".

Oscar voters outside of Los Angeles and New York will now also be sent vouchers giving them free access to commercial screenings.

There have been complaints that those voters outside areas where studios hold free previews had trouble seeing all the movies necessary to make informed decisions.