For at least six years, law enforcement officials working on a counternarcotics program have had routine access, using subpoenas, to an enormous AT&T database that contains the records of decades of Americans’ phone calls — parallel to but covering a far longer time than the National Security Agency’s hotly disputed collection of phone call logs.

The Hemisphere Project, a partnership between federal and local drug officials and AT&T that has not previously been reported, involves an extremely close association between the government and the telecommunications giant.

The government pays AT&T to place its employees in drug-fighting units around the country. Those employees sit alongside Drug Enforcement Administration agents and local detectives and supply them with the phone data from as far back as 1987.

The project comes to light at a time of vigorous public debate over the proper limits on government surveillance and on the relationship between government agencies and communications companies. It offers the most significant look to date at the use of such large-scale data for law enforcement, rather than for national security.

The scale and longevity of the data storage appears to be unmatched by other government programs, including the N.S.A.’s gathering of phone call logs under the Patriot Act. The N.S.A. stores the data for nearly all calls in the United States, including phone numbers and time and duration of calls, for five years.

Hemisphere covers every call that passes through an AT&T switch — not just those made by AT&T customers — and includes calls dating back 26 years, according to Hemisphere training slides bearing the logo of the White House Office of National Drug Control Policy. Some four billion call records are added to the database every day, the slides say; technical specialists say a single call may generate more than one record. Unlike the N.S.A. data, the Hemisphere data includes information on the locations of callers.

The slides were given to The New York Times by Drew Hendricks, a peace activist in Port Hadlock, Wash. He said he had received the PowerPoint presentation, which is unclassified but marked “Law enforcement sensitive,” in response to a series of public information requests to West Coast police agencies.

The program was started in 2007, according to the slides, and has been carried out in great secrecy.

“All requestors are instructed to never refer to Hemisphere in any official document,” one slide says. A search of the Nexis database found no reference to the program in news reports or Congressional hearings.

The Obama administration acknowledged the extraordinary scale of the Hemisphere database and the unusual embedding of AT&T employees in government drug units in three states.

But they said the project, which has proved especially useful in finding criminals who discard cellphones frequently to thwart government tracking, employed routine investigative procedures used in criminal cases for decades and posed no novel privacy issues.

Crucially, they said, the phone data is stored by AT&T, and not by the government as in the N.S.A. program. It is queried for phone numbers of interest mainly using what are called “administrative subpoenas,” those issued not by a grand jury or a judge but by a federal agency, in this case the D.E.A.

Relying on one of our royal corporations to store and dole out information on every citizen smacks of one more sci-fi prediction come true.