Trump chief of staff John Kelly backed off his effusive praise of a top aide accused of domestic abuse, underlining the intense scrutiny the retired Marine four-star general is facing as the White House contends with the latest turmoil.

White House staff secretary Rob Porter, a key ally of Kelly in controlling information flow to President Donald Trump, said Wednesday he plans to resign after two ex-wives accused him of physical and emotional abuse. Porter, who could leave the White House as early as Thursday, denied the allegations, which were initially reported by the British tabloid Daily Mail.

Kelly, who became chief of staff in July after a short stint as secretary of Homeland Security, is widely cited for bringing a measure of discipline to Trump's West Wing, which was plagued by leaks and general chaos during the tenure of previous chief of staff Reince Priebus.

However, there have been reports of tension between the freewheeling Trump and the buttoned-up Kelly, and the chief of staff has brought criticism on himself for some of his remarks and actions. Kelly, an immigration hardliner, played a key role in killing a bipartisan immigration deal last month, which led to a three-day partial government shutdown. This week, he drew fire for calling some immigrants "too lazy to get off their asses" for not signing up for federal protections.

Kelly's handling of the Porter situation, including reports that he knew about the allegations for month, has only intensified the scrutiny on his performance.

At first, Kelly praised Porter to the Daily Mail, hailing him as a "trusted professional" and a friend. "I am proud to serve alongside him," Kelly added. CNN reported that Kelly and White House communications director Hope Hicks collaborated on formulating a supportive response for the staff secretary. The report and the Daily Mail said Hicks is romantically involved with Porter.

However, in a statement Wednesday night, Kelly said he was "shocked" by the allegations against Porter, although he did not denounce his aide outright.

"There is no place for domestic violence in our society. I stand by my previous comments of the Rob Porter that I have come to know since becoming Chief of Staff, and believe every individual deserves the right to defend their reputation," Kelly said. "I accepted his resignation earlier today, and will ensure a swift and orderly transition."

CNN reported that Kelly and other top Trump aides knew in early fall that Porter was accused of domestic abuse, creating difficulties in getting him a security clearance.

The Washington Post, meanwhile, reported that Kelly actually tried to talk Porter out of resigning on Tuesday, when the Daily Mail first published the allegations. Porter decided to quit Wednesday after photos of ex-wife Colbie Holderness' black eye emerged.

Two White House officials told The New York Times that Porter had misled Kelly about the severity of the abuse allegations, saying that the women made up stories.

A White House spokeswoman didn't immediately respond to CNBC's request for comment about senior White House staffers' knowledge of the allegations.