Thompson won a best actress Oscar for Howard's End

Thompson, who won the award in its inaugural year with the Cambridge Footlights, added her voice to the campaign on Tuesday.

"The Perrier Awards should be boycotted by all right-thinking people because Nestl� has got to be stopped," Thompson said through her agent on Tuesday.

A number of celebrities have publicly asked comedians not to enter the competition because of Nestl�'s sales of powdered baby milk in the Third World.

Campaigners believe that breast-feeding should be encouraged in developing countries as bottle-fed babies are more likely to die of water borne infections.

Allegations

Nestl� has rejected the criticisms, saying it promotes infant foods in line with World Health Organisation codes of conduct.

"Many of the allegations made about our behaviour are years out of date and have long since been rectified," the company said in a statement issued in London.

A number of other celebrities including Julie Walters, Richard E Grant and pop bands Pulp and Ocean Colour Scene are backing the lobbying group Baby Milk Action.

Rich Hall saw off competition from 140 other acts in 2000

The group wants to increase pressure on the food firm by persuading as many top comedians as possible not to enter the Perrier competition.

American comedian Rich Hall scooped the coveted Perrier Comedy award in 2000.

The prize, which is in its 20th year, is awarded to the most original and funny cabaret, revue or comedy act at the fringe.

Other Perrier winners, including Steve Coogan, Frank Skinner, Lee Evans, Sean Hughes, and The League of Gentlemen, have gone on to win wider recognition.

The awards have been running since 1981 when the Cambridge Footlights, which included Stephen Fry and Emma Thompson, won the inaugural contest.

To be eligible for the awards, acts must be original and fall into the cabaret, comedy, revue or stand-up category.