(CNN) Rep. Elijah Cummings on Sunday afternoon slammed Donald Trump for his frequent claim that the controversy over Hillary Clinton's email was "bigger than Watergate."

"Unfortunately, Donald Trump and his associates have blown this thing up like Director Comey should have known," Cummings, a Maryland Democrat, told CNN's Wolf Blitzer on "Situation Room." "You know, Donald Trump saying this is worse than Watergate and he didn't even know what the hell he was talking about."

Earlier in the interview, Cummings, who is the ranking member on the House Committee on Oversight and Government Reform, called FBI Director James Comey an honorable man but said he had erred in notifying Congress about the new tranche of emails discovered on Anthony Weiner's laptop.

"This should have never happened. ... I don't think that the director should have come out last week and put out that very vague letter and I think it was a mistake."