The former Port Authority official who personally oversaw the lane closings at the George Washington Bridge, central to the scandal now swirling around Gov. Chris Christie of New Jersey, said on Friday that “evidence exists” that the governor knew about the closings when they were happening.

A lawyer for the former official, David Wildstein, wrote a letter describing the move to shut the lanes as “the Christie administration’s order” and said “evidence exists as well tying Mr. Christie to having knowledge of the lane closures, during the period when the lanes were closed, contrary to what the governor stated publicly in a two-hour press conference” three weeks ago.

During his news conference, Mr. Christie specifically said he had no knowledge that traffic lanes leading to the bridge had been closed until after they were reopened. “I had no knowledge of this — of the planning, the execution or anything about it — and that I first found out about it after it was over,” he said. “And even then, what I was told was that it was a traffic study.”

The letter, which was sent as part of a dispute over Mr. Wildstein’s legal fees, does not specify what the evidence is. Nonetheless, it marks a striking break with a previous ally. Mr. Wildstein was a high school classmate of Mr. Christie’s who was hired with the governor’s blessing at the Port Authority of New York and New Jersey, which controls the bridge.