The reality star has responded to the television network's claim that they didn't fire him from an upcoming TV show because of his recent diagnosis with multiple sclerosis by calling it ''Bull-F*****g-S***t'' and urging people to boycott the channel.
Jack angrily tweeted: ''I took part in a 16 hr challenge over 30 miles with a 40lbs ruck on my back in Jan. I had MS then. Don't tell me wot physically demanding is'' (sic)
He added: ''NBC said they didn't fire me over my diagnosis? Bull-F*****g-S***t#BoycottNBC''.
Sharon Osbourne caused controversy yesterday (06.08.12) when she announced she was quitting her role on 'America's Got Talent' because the network had ''discriminated'' against her son.
She claimed he was unfairly dropped from new reality show 'Stars Earn Stripes', which will see celebrities compete in demanding military-style challenges.
NBC chairman Bob Greenblatt commented: ''Although we did not ask Jack to participate in the competition, we were able to offer him two substantial alternative roles on the show, both of which he declined.
''This network does not discriminate on any basis.''
But Jack - who has four-month-old daughter Pearl with fiance Lisa Stelly - is adamant the channel's decision was a deliberate snub because of his degenerative condition.
His fiance also urged for an NBC boycott, tweeting: ''Liars! bull-f****g-s**- boycott NBC''.