Richard Gabel, 84, a retired government economist and consultant whose writings played a role in the government's landmark antitrust case against AT&T, died of respiratory failure Aug. 1 at Inova Fairfax Hospital. He lived in Arlington.

Mr. Gabel often worked at the nexus of economics and telecommunications. As a Brookings Institution fellow, he had written "Development of Separations Principles in the Telephone Industry" (1967), a book that explored costs and pricing arrangements of local and long-distance telephone service providers.

After retiring in 1974 from a dual position on the Council of Economic Advisers and as a Commerce Department economist, he began working as a consultant to the Justice Department's antitrust division. The division was preparing a case that led to the divestiture of AT&T. Much of his language in papers he prepared for the case appeared in the Justice Department memorandum as basis for legal motions.

Mr. Gabel was a New York native and a 1940 economics graduate of City College of New York. He received a master's degree in economics from Columbia University in 1941. He was an Army Signal Corps veteran of World War II.

From 1946 to 1949, he was an economist at the Federal Communications Commission. He spent the next decade at the Rural Electrification Administration, where he helped establish the engineering standards for constructing rural telephone systems.

From 1959 to 1966, he was director of telecommunications at the General Services Administration.

From 1969 to 1971, he worked in the White House Office of Telecommunications Policy as a senior economist and was on President Richard M. Nixon's task force on communications policy.

As a private consultant until 1997, Mr. Gabel represented consumer interests in state telephone cases.

He was a member of Temple Beth-El in Alexandria and a former chairman of Arlington's Public Utilities Commission.

He played competitive handball until he was 78.

Survivors include his wife of 62 years, Louise Kohn Gabel of Arlington; four children, Susan Poretz of Great Falls, Jon Gabel of Annandale and Carol Berlin and David Gabel, both of Newton, Mass.; a brother; nine grandchildren; and six great-grandchildren.