With Congress poised for a final vote on the energy bill, the Environmental Protection Agency made an 11th-hour decision Tuesday to delay the planned release of an annual report on fuel economy. But a copy of the report, embargoed for publication Wednesday, was sent to The New York Times by a member of the E.P.A. communications staff just minutes before the decision was made to delay it until next week. The contents of the report show that loopholes in American fuel economy regulations have allowed automakers to produce cars and trucks that are significantly less fuel-efficient, on average, than they were in the late 1980's. The average 2004 model car or truck got 20.8 miles per gallon, about 6 percent less than the 22.1 m.p.g. of the average new vehicle sold in the late 1980's, according to the report. Releasing the report this week would have been inopportune for the Bush administration, its critics said, because it would have come on the eve of a final vote in Congress on energy legislation six years in the making. The bill, as it stands, largely ignores auto mileage regulations.