Under the Bush administration, the federal government has aggressively used a well-established tool of public relations: the prepackaged, ready-to-serve news report that major corporations have long distributed to TV stations to pitch everything from headache remedies to auto insurance. In all, at least 20 different federal agencies, including the Defense Department and the Census Bureau, have made and distributed hundreds of television news segments in the past four years, records and interviews show. Many were subsequently broadcast on local stations across the country without any acknowledgement of the government's role in their production.