"The Tonight Show" host Jay Leno called NBC executives "snakes" in Monday's monologue. Reuters

Long-time “Tonight Show” host Jay Leno launched another attack on NBC executives on Monday, prompting increased speculation about his feud with network brass.

During Monday’s “Tonight Show” monologue, Leno turned a St. Patrick’s Day joke into a mockery of the so-called “snakes” in the NBC front office.

"Well, you know the whole legend of St. Patrick, right?" Leno said. "St. Patrick drove all the snakes out of Ireland, and then they came to the United States and became NBC executives." The punch line drew gasps and applause from the show’s studio audience.

Leno’s latest attack comes on the heels of Leno’s inflammatory Feb. 28 monologue in which he mocked NBC’s ongoing ratings struggles.

"For the first time in history, NBC is going to finish fifth in the ratings period," Leno said. "We are behind the Spanish-language network Univision -- or as we call it here in Los Angeles: Cinco de Ratings." He then added, "It's so bad 'The Biggest Loser' isn't just a TV show anymore; it's our new motto."

The incendiary jokes reportedly led to a heated email exchange between Leno and top NBC executive Robert Greenblatt, the New York Times reported. Apparently, the emails came as a surprise to Leno, who defended his comments by citing the long-standing precedent of late-night hosts using “their masters” as comedic fodder, according to a New York Times source.

As the relationship between Leno and network brass deteriorates, speculation that NBC is planning to replace the veteran host with youthful “Late Night” host Jimmy Fallon abounds. The Hollywood Reporter suggests that the network is planning to announce the lineup change in May, although NBC has yet to substantiate the claim of his retirement.

The move would reportedly be an attempt to stave off potential ratings gains for ABC late-night host Jimmy Kimmel, who recently moved his show to the same time slot as “The Tonight Show” and grows more popular by the day.