"I trusted him before, but I can't now," said five-term Rep. Lee Terry, whose district includes metropolitan Omaha.
Gonzales' credibility took a blow this past week during testimony by his former chief of staff, Kyle Sampson, before the Senate Judiciary Committee. Sampson, who resigned March 12, said the attorney general was regularly briefed about plans to fire the prosecutors and was involved with discussions about "this process of asking certain U.S. attorneys to resign."
Lawmakers impatient to hear Gonzales' side of the story said the embattled attorney general needed to explain himself quickly or risk more damage to his department.
Gonzales is to testify on Capitol Hill on April 17.
"My views were that this was Democrat posturing and a witch hunt," Terry said. "My trust in him in that position has taken a hit because of these contradictory statements by him."
Terry's change of heart came on the first day of a two-week break for House members, and Republicans hoped to avoid spending much of that time on the defensive about Gonzales.
Gonzales on Friday sought to explain weeks of inconsistencies about how closely involved he had been in decisions to dismiss the U.S. attorneys.
He said he had been aware his staff was drawing up plans for the firings but did not recall taking part in discussions over which people would actually be told to go.
"I believe in truth and accountability, and every step that I've taken is consistent with that principle," Gonzales said in Boston. "At the end of the day, I know what I did. And I know that the motivations for the decisions that I made were not based upon improper reasons."
Asked why he had not resigned, as some Democrats and Republicans have demanded, he said: "I am fighting for the truth."
Terry, asked whether he believed Gonzales' accounts, said: "I don't know ... I don't think so. ... I trusted him before, but I can't now."
He added, "Frankly, until these statements came out that contradicted his first statement, I was backing him, saying that he shouldn't resign. Now I think that he should."
Meanwhile, Sen. Charles Schumer, D-N.Y., is demanding a retraction from Gonzales on behalf of New Mexico's former U.S. attorney, who was among the prosecutors fired last year.
Schumer wrote Gonzales on Friday demanding that the attorney general clear David Iglesias' name.
Schumer's letter came the day after Sampson testified that in hindsight, he would not have recommended Iglesias for dismissal.