WASHINGTON --- Sen. Saxby Chambliss -- already facing heat for sharply questioning a whistleblower in a fatal sugar refinery accident outside Savannah -- toughened his criticism by saying the employee is "on the hook" for the February explosion that killed 13 workers.

Asked about the issue in the Capitol on Friday, the Georgia Republican suggested that the whistleblower is trying to deflect from his own failure to act by accusing Imperial Sugar Co. executives of resisting safety warnings about the company's plant in Port Wentworth, Ga.

Mr. Chambliss said if vice president of operations Graham H. Graham knew the plant was so dangerous, he should have pressed more urgently.

"My question is if it was that bad, and you thought somebody was fixing to get killed, why in the world weren't you more forceful?" he said. "Why didn't he really do something? Because ... as a result of his failure to do something, a serious accident did happen, in my opinion."

"This guy Graham knows he's on the hook," Mr. Chambliss added.

Mr. Chambliss, who works closely with the sugar industry as the top-ranking Republican on the Senate Agriculture Committee, insists he is not trying to defend Imperial, which is among the largest U.S. sugar producers.

But his comments are the latest in which he has focused on Mr. Graham as a culprit instead of the company, despite a recent government investigation that accused Imperial of willfully and egregiously violating dozens of safety standards.

Mr. Graham's supporters emphasize that Mr. Graham had worked at Imperial for just three months before the accident.

Mr. Graham's attorney, Philip Hilder, called Mr. Chambliss' criticism "absolutely nonsensical."

"That plant has existed for some 90 years before Mr. Graham came," Mr. Hilder said. "He was diligent in addressing the problems and got pushback from upper management, and for the senator ... to suggest that he joined the company just a matter of weeks before the explosion and that fault lies with him -- even though he saw the problem and tried to rectify it -- is just the height of irresponsibility."

Mr. Hilder and others had accused Mr. Chambliss of doing the company's bidding Tuesday when he sharply questioned Mr. Graham at a Senate hearing. Mr. Chambliss' questions raised eyebrows, because no one aside from Imperial had publicly doubted Mr. Graham's claims. That includes Mr. Chambliss' fellow Georgia Republican Johnny Isakson. The two rarely split, but Mr. Isakson says he has full faith in Mr. Graham's account.

Some of Mr. Chambliss' questions at the hearing were similar to a line of questioning that Imperial had suggested to lawmakers, but Mr. Chambliss said Friday he never saw any questions suggested by Imperial.

Mr. Chambliss also said he has not been influenced by any lobbyists for the Sugar Land, Texas-based company or by his son, Bo. The younger Mr. Chambliss is an in-house Washington lobbyist for the Chicago Mercantile Exchange, which also is represented by an outside firm that lobbies for Imperial Sugar.