Porter called the allegations "outrageous" and "simply false." In a statement, he said he had taken the pictures that Holderness provided to The Intercept and that "the reality behind them is nowhere close to what is being described."
"I have always put duty to country first and treated others with respect," Porter said in a statement. "I am deeply grateful for the opportunity to have served in the Trump administration and will seek to ensure a smooth transition when I leave the White House."
Holderness did not respond to attempts to contact her by telephone and email.
Kelly's first statement on Porter complimented him without mentioning the allegations.
"Rob Porter is a man of true integrity and honor and I can't say enough good things about him," Kelly said. "He is a friend, a confidante and a trusted professional. I am proud to serve alongside him."
Several White House aides said Wednesday that Kelly's statement was a mistake. But Kelly has leaned heavily on Porter since becoming chief of staff in July, and considers the staff secretary to be a close and trusted confidante, they said.
The Daily Mail has recently delved into Porter's personal life, reporting last week -- complete with paparazzi-style photos -- that he was in a romantic relationship with another of Trump's most senior aides, White House Communications Director Hope Hicks.
Kelly assigned Porter to help bring more discipline to the West Wing by ensuring that no staff memos, policy documents, correspondence or news articles reached Trump's desk without careful inspection. He almost always accompanied the president when he traveled, and frequently could be seen near Trump as he boarded Marine One and Air Force One.
He was one of a handful of aides who helped to write the president's first State of the Union address. As an assistant to the president, Porter was paid the top White House staff salary of $179,000.
(Margaret Talev and Ari Natter contributed to this report)
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