(CNN) The top Democrat on the House Oversight and Government Reform Committee argued Commerce Secretary Wilbur Ross was part of a "secret campaign" to push for a citizenship question to be added to the 2020 Census.

Maryland Rep. Elijah Cummings, who could be the next chairman of the committee if Democrats win the majority this fall, was responding to the Department of Justice acknowledging Thursday that the idea of the citizenship question came from Trump advisers, including former adviser Steve Bannon, rather than the Justice Department.

"The Department of Justice has a direct and clear conflict of interest," Cummings said in a statement. "Based on this new evidence, it is now clear that both the Justice Department and the White House were part of Secretary Ross' secret campaign to orchestrate the addition of a citizenship question to the census. But now the Justice Department is trying to block depositions for the very same Trump Administration officials who engaged in these actions — and then misled Congress. The Trump Administration should not be using the levers of justice to conceal its own wrongdoing."

The Justice Department revelations came after Ross testified before a House panel in March that it was the department that "initiated the request for inclusion of the citizenship question." And while responding to a question from Rep. Grace Meng, a New York Democrat, Ross said he was not aware of any discussions with White House advisers before he began looking into the idea.

"Has the President or anyone in the White House discussed with you or anyone on your team about adding this citizen question," Meng asked.

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