The U.S. Chamber of Commerce, the 100-year-old big business group, spent more than $20 million on lobbying in the first quarter of the year, nearly double what it spent in the corresponding period of 2011, according to just-filed reports with Congress.

The chamber’s quarterly lobbying bill during the height of the health care debate at the end of 2009 soared to $71 million, cementing its reputation as the biggest spender on K Street. This year, issues such as an overhaul of the tax code, a jobs bills, highway funding and tort reform helped fuel the chamber’s legislative portfolio, according to the 62-page report filed today with the House and Senate. All first-quarter reports are due at midnight.

Chamber spokeswoman Blair Latoff said the group files Lobbying Disclosure Act reports under a method also used for the Internal Revenue Service, which requires disclosure of money spent on issue advocacy ads. Many other lobby groups avoid the method.

“In our mind it is more transparent,” Latoff said.

The chamber, she added, ran ads in the first quarter against the health care law — which is facing a constitutional challenge at the Supreme Court — as well as on tax, energy and travel and tourism matters.

Other big spenders on K Street during the first quarter included the Pharmaceutical Research and Manufacturers of America, the prescription drug lobby, which reported spending $5.3 million, up from last year’s first quarter filing of $4.5 million. The American Medical Association reported spending $4.7 million, an increase from $4.3 million at the same time last year. And defense and aerospace giant Boeing Co., which has been furiously lobbying for a reauthorization of the Export-Import Bank, reported spending $4.1 million, about the same as in the first quarter of 2011.

Business for outside firms seems to be holding steady, the filings show.

K Street’s biggest shop, Patton Boggs, reported a slight dip for the first quarter, bringing in $12.2 million, compared with $12.3 million in last year’s first quarter.

But some of the city’s largest practices experienced solid growth. And many lobbyists say they are optimistic about the rest of this year, with a potentially active lame-duck session of Congress on the horizon after Election Day.

Alston & Bird reported $3.3 million for the first quarter, up from $3.1 million for the first three months of last year. K&L Gates improved, too, bringing in $4.7 million in the most recent filing period over last year’s first quarter tally of $4.6 million.

With tax cuts expiring and automatic spending cuts looming at year’s end, lobbyists say clients are not cutting back as much as they might ordinarily in a presidential election year when Capitol Hill is largely gridlocked.

“The thing is when you get one of these big games at the end of the year, all the power tends to focus narrowly on the leadership,” said K&L Gates lobbyist Jim Walsh, a former Member of Congress.

Leaders often turn to committee chairmen for policy proposals that have already been vetted, he said.

“In order to get them in the playbook, you need to start early,” Walsh said. “And that’s what we’re telling our clients, and they’re buying into that.”

Ogilvy Government Relations saw an even bigger uptick, reporting $5 million for the quarter, up from last year’s $4.5 million.

“The concern over a very aggressive lame-duck session as well as a very aggressive legislative calendar for next year, is creating a platform for this year for a lot of groundwork to be laid,” said Ogilvy’s Drew Maloney. “Companies that are committed to a longterm strategy to manage their political risk are staying engaged in preparation for the lame duck and next year.”

One of Ogilvy’s clients, the private equity firm Blackstone Group, paid it $1.3 million for the quarter —one of the single biggest lobbying contracts, according to the filings.

“They’re a global company with many issues, so we monitor and advocate on many issues for them,” Maloney said.

The actual amount of money spent on lobbying wasn’t as heavy as documented in the reports, according to company executives and firms.

The DCI Group filed a report stating that it had brought in $1 million from Verizon Communications Inc., only to later make a second filing that scaled back the quarterly fee to $100,000.

And even though Purdue Pharma is dealing with a lot of legislative issues surrounding its pain drug Oxycontin — such as H.R. 4956, the Stop Oxy Abuse Act — it hasn’t actually spent $3 million to lobby as it originally reported to Congress. The Stamford, Conn., company’s spokesman, Jim Heins, wrote in an email that his colleagues “believe that there was indeed a reporting error” and that the company intended to report spending $300,000 and would look into filing an amended report with one less zero.