CELEBRITY chef Darren Simpson has been labelled a "sell-out" and "a laughing stock" by his peers for creating a burger range for fast-food giant KFC.

Television advertisements showing the La Scala chef spruiking his Signature Burger line for KFC have sparked a barrage of criticism and backlash from Sydney's leading restaurateurs and the public.

Four In Hand chef Colin Fassnidge openly mocked the endorsement deal, saying the Ready Steady Cook regular was now a laughing stock.

"If you read Twitter, he's destroyed - he's a laughing stock," Mr Fassnidge said.

"If I'm promoting through my restaurant good eating and good quality food, to then promote s..t basically that I wouldn't give to my kids, then that's a double standard."

It's the first time an Australian celebrity chef has put their name to a food range with a major fast-food chain.

In the ads, which first screened last week, Simpson visits a poultry farm before preparing one of two $6.95 chicken burgers he's developed for the limited-edition range.

KFC claims the new burgers are made from 100 per cent free-range chicken breast - but a footnote at the bottom of the ad reads "excludes emergency stock".

Simpson defended his decision to partner with KFC, saying his peers were too quick to criticise.

"I'm not sure how many of these critics have actually tried my burgers, but I think they should do that before passing judgment," he said yesterday.

"People are quick to label fast food as junk, so it's a bit odd there is now criticism of a real effort to improve the quality of it.

"I'm pleased to be the first chef to get on board to try to do that. As far as I'm concerned, that is a positive thing."

A KFC spokesman said nutritional values for the burgers had not been finalised but they had "less fat and kilojoules than a Whopper With Cheese".

According to Hungry Jack's, its Whopper With Cheese contains 3229kj, almost a third of an average adult's recommended daily dietary intake.

Mr Fassnidge said chefs could make a fortune from endorsement deals but they also put their credibility on the line.

Merivale's Dan Hong posted on Twitter: "He was never really a respected chef in the first place, so who cares?"

Members of the public also expressed outrage on Twitter, with one user posting: "Darren Simpson you complete and utter sell-out. KFC? Seriously?"

However, other top chefs, including Marque's Mark Best and Rockpool's Neil Perry, were quick to defend Simpson on the social networking site.

Best tweeted on Friday: "Dazza is just a nice Irish lad trying to make his way in the big smoke. Judge not ... "