The White House eliminated the position of cybersecurity coordinator on the National Security Council on Tuesday, doing away with a post central to developing policy to defend against increasingly sophisticated digital attacks and the use of offensive cyber weapons.

A memorandum circulated by an aide to the new national security adviser, John R. Bolton, said the post was no longer considered necessary because lower-level officials had already made cybersecurity issues a “core function” of the president’s national security team.

Cybersecurity experts and members of Congress said they were mystified by the move, though some suggested Mr. Bolton did not want any competitive power centers emerging inside the national security apparatus.

The decision was criticized by Mark R. Warner, a senator from Virginia and the ranking Democrat on the Senate Intelligence Committee. “I don’t see how getting rid of the top cyber official in the White House does anything to make our country safer from cyber threats,” he wrote on Twitter.