And while Mr. Obama has imposed restrictions on hiring lobbyists for government posts, the administration has used waivers and recusals more than two dozen times to appoint lobbyists to political positions. Two lobbyists also cited instances in which the White House had suggested that a job candidate be “deregistered” as a lobbyist in Senate records to avoid violating the administration’s hiring restrictions.

A senior White House official, speaking on the condition of anonymity, said that in “a small number of cases,” people might have been “wrongly” registered as lobbyists, based on federal standards. The official said that while the White House might have discussed such instances of possible “over-registration,” he was “quite confident that no lobbying shop has been instructed to deregister anyone.”

Many lobbyists still get in the front door at the White House  nearly 1,000 times, according to a New York Times examination of public White House visitors’ logs and lobbying registration records.

Those logs, though, present an incomplete picture. For instance, many of the entries do not reflect who actually took part in a meeting. The “visitee” often shows up not as the White House official who was the host, but as the administrative assistant who arranged the meeting.

David Wenhold, president of the American League of Lobbyists, based in Washington, said the current “cold war” relationship between the White House and K Street lobbyists was one of mutual necessity, with the White House relying on lobbyists’ expertise and connections to help shape federal policies.

“You can’t close the door all the way because you still need to have these communications,” Mr. Wenhold said. “It makes a great sound bite for the White House to demonize us lobbyists, but at the end of the day, they’re still going to call us.”

Lobbyists say some White House officials will agree to an initial meeting with a lobbyist and his client at the White House, but then plan follow-up sessions at a site not subject to the visitors’ log.