Lobbying spending by the largest business group plunged in 2011 by more than half from a year earlier in a reflection of gridlock in Congress and the calm before a major campaign year, records show.

The Chamber of Commerce spent $44.2 million on lobbying last year, according to reports filed with Congress. A report for the final three months of the year became available on Friday.

The total is a big drop from the $100.2 million that the chamber spent in 2010, when it paid for ads ahead of midterm U.S. elections. In 2009, when there was no election, it spent a record $123.3 million as major legislative battles over healthcare and financial regulation consumed Washington.

The level of activity in 2011 was consistent with previous non-election years, said chamber spokesman J.P. Fielder.

During 2007, the most recent year before a presidential election year, the chamber reported $30.1 million in lobbying.

The large swings in reported spending may be explained by the intricacies of U.S. lobbying law, said Craig Holman, a lobbyist for consumer group Public Citizen.

He said the huge drop in the chamber's reports likely reflects a shift during 2011 from legislative to regulatory activity, which does not always need to be disclosed.

Much of that lobbying activity is not reportable, Holman said.

Public Citizen, which is often at odds with the chamber over policy, reported $200,000 in 2011 lobbying expenses, compared to $160,000 in 2010 and $200,000 in 2009.

Chamber president Thomas Donohue told reporters this month to expect record-breaking spending in 2012 in support of a vigorous outreach to voters in congressional races.

In the past year, the chamber won on its request of Congress to pass trade agreements with Colombia, Panama and South Korea.

But it fell short of achieving other goals, including the Keystone XL pipeline from Canada to Texas, a tax holiday on the overseas profits of U.S. companies, and greater protection for U.S. intellectual property from online piracy.

It wrestled with lawmakers to raise the U.S. debt limit and to cut back on what it considered excessive regulation.

These are policies that, if enacted, will help grow the economy and create jobs, without increasing the deficit, Fielder said.

Its legal arm, the U.S. Chamber Institute for Legal Reform, separately reported spending $21.6 million on lobbying during 2011 on subjects such as arbitration and anti-fraud measures.

(Editing by Kevin Drawbaugh and Tim Dobbyn)