Porter denied the allegations in a statement issued in the wake of his resignation on Wednesday, reports CNN.
“These outrageous allegations are simply false,” he said in his statement.
“I have been transparent and truthful about these vile claims, but I will not further engage publicly with a coordinated smear campaign.”
Porter resigned over the objections of White House Chief of Staff John Kelly and others, a White House official said.
However, Kelly said: “Rob Porter is a man of true integrity and honour and I can’t say enough good things about him. He is a friend, a confidante and a trusted professional. I am proud to serve alongside him.”
The allegations were first reported by the Daily Mail earlier this week, CNN reported.
Porter has been dating White House communications director Hope Hicks, one of the most influential figures in the West Wing, several people familiar with their relationship have said.
His last day at the White House has not yet been set, according to White House press secretary Sarah Sanders, who added that Porter will stay on to ensure a smooth transition to his successor.
Porter, a graduate of Harvard Law School and a Rhodes scholar, previously worked for Republican Senators Orrin Hatch, Rob Portman and Mike Lee.
Porter joined the White House at the beginning of Trump’s administration.
As staff secretary, Porter’s responsibility was mainly in the flow of paper that crossed
Trump’s desk, including the wave of executive orders and actions that Trump inked during the first months of his tenure. A lawyer, Porter also participated in the process of legal vetting the myriad documents that require the President’s signature.