'Modern Family' Producers -- Accused of Screwing the Pooch

"Modern Family" producers have secretly replaced one of the biggest stars on the show, TMZ has learned -- but the crazy part ... you probably wouldn't have noticed if we didn't tell you ... THE DOG!!!!

Sources connected with production tell TMZ, the French bulldog who plays Stella -- Jay Pritchett's pooch -- recently got the boot ... and has been replaced by a lookalike for next season.

According to sources, the dog who formerly played Stella -- real name Brigitte -- had been hired by an Hollywood animal agency called Good Dog Animals, which then subleased Brigitte to the "Modern Family" production shortly before Season 2.

We're told everything went great for 2 seasons, but GDA recently decided it no longer wanted to work with Brigitte -- so it unceremoniously dumped the dog in favor of its own lookalike Frenchie ... some bitch named Beatrice.

"Modern Family" then hired Beatrice instead.

Now, like scores of red-blooded Americans ... Brigitte is unemployed and hoping to find another job.