The broadcaster admonished a leading organiser of Momentum, James Schneider, saying that Corbyn's manifesto of policies was "hot air unless you can get elected".
Boulton also reminded Schneider that prominent Labour MPs, a substantial number of whom took part in a mass resignation from the Shadow Cabinet, were telling Corbyn he could not win a general election.
"What you want to do is keep a loser in charge of the Labour Party," the Sky stalwart fired at Schneider.
To the Momentum leader who responded that Corbyn was "not a loser", an insistent Boulton re-affirmed: "He is a loser."
Schneider hit back, saying the idea that Corbyn was responsible for a Brexit win in the EU referendum campaign, despite having campaigned for 'Remain', was "fatuous".
Boulton responded, calling an end to the interview: "Says you, or is it ten or eleven members of the shadow cabinet? Or is it twelve now?"
The interview took place on Sunday, when news of multiple resignations from the shadow frontbench began to break.
Eleven MPs stepped down from serving alongside Corbyn on Sunday, precipitated by the leader firing shadow foreign secretary Hilary Benn amid reports he was behind a coup to unseat the leader.