The pair, along with Piers Morgan discussed a potential upcoming leadership election, and Iain reassured those watching that he was firmly behind the current Prime Minister Theresa May.
The MP explained: “I agree with David Davis that it would be a catastrophe if we had a leadership election right now.
“My general view is that the Tory government and if they need to discuss their desire for a re-election, they need to do so in a dark room.
“You don’t have to go to the newspapers to communicate!” Duncan Smith joked.
As Piers Morgan, 52, asked if the former secretary of state for work and pensions was suggesting there was some “scheming and plotting” in the party, Duncan Smith was quick to defend the Tories, snapping back: “It would not happen in my party.”
However, Susanna Reid, 46, was quick to make light of the situation, joking: “Your party is the worst for scheming and plotting!”
This came after the pair clashed with the housing minister earlier in the show over the Grenfell fire.
Alok Sharma faced a grilling from Morgan as he failed to answer with a straight yes or no about whether the cladding used in the tower was illegal or not.
Good Morning Britain airs weekdays on ITV from 6am.