WASHINGTON — Companies, unions and other interests spent $849 million on federal lobbying in July, August and September, more than in any quarter since lobbyists began filing quarterly reports at the beginning of last year, according to a nonpartisan group that monitors political expenditures.

Lobbying spending has totaled $2.5 billion so far this year, slightly exceeding the total for all of 2005, said the Center for Responsive Politics.

The massive sums — covering the activities of 13,428 lobbyists — are being spent despite efforts by President Barack Obama to curb the clout of Washington's influence industry, and reflect the administration's and Congress' ambitious efforts on health care and other areas.

By far the biggest individual spender for lobbying has been the U.S. Chamber of Commerce, at $65 million. Closest to it are Exxon Mobil Corp., at $21 million, and the Pharmaceutical Research and Manufacturers of America and General Electric Co., both at $20 million.

Divided into sectors of the economy, companies and other groups involved in health care have led the way, spending $397 million for the first nine months of the year. That's about a 9 percent increase over the same period a year ago.

Besides the pharmaceutical association, the biggest lobbying spenders in this category include $16 million by Pfizer Inc.; $12 million by the American Medical Association; and $11 million by the American Hospital Association.

Other sectors that have seen the heaviest lobbying spending are general business, $363 million; finance, insurance and real estate, $335 million; and energy and natural resources, $301 million.

The AFL-CIO has outspent all other labor organizations this year, with expenditures of nearly $3 million.