"That's not a service to the campaign", Trump Jr. speech/" target="_blank">said.
Trump Jr. accused Lewandowski of bad mouthing the campaign to reporters - and making up details about private campaign strategy meetings.
Trump's campaign was hoping Tuesday's formal nomination of the candidate would bring an end to the divisions within the Republican Party, and would shift the spotlight away from the plagiarism controversy over Monday night's address by Trump's wife Melania.
Asked if Manafort should be held accountable, Mr Lewandowski said: "Hey, I was sacked so anything can happen in this life".
"When you do something that is so egregious that the story today is not how great Melania Trump was, and how successful this convention is going to be, but is because a staff person didn't do their job properly, there absolutely has to be accountability. And she put those thoughts together so she could talk about her husband", Lewandowski said.
"I want to be very clear", Lewandowski said.
During Tuesday's breakfast, Rep. Peter Roskam said that he didn't expect an apology from "anyone whose name rhymes with Trump." Rep.
Meanwhile, the former Trump campaign manager said that if anyone should be fired following this speech scandal, it would have to be the man who took over his role, Paul Manafort.
Asked point-blank of the buck stops with the guy who replaced him, Lewandowski shot back, "Well, I can tell you when I was the campaign manager, the buck stopped with me, and I'm sitting here with CNN now".
Ultimately, Lewandowski said the response was up to Trump. "If it was Paul Manafort, he should do the right thing and resign".
Aides say that Lewandowski's presence at the Republican National Convention is to create the perception that he still has influence inside the campaign. "I think they fell in love with her and she's going to make an incredible first lady". "To think that she would be cribbing Michelle Obama's words is insane", Manafort said.