Despite the flurry of oil-spill-related activity on Capitol Hill, BP reported sharply reduced lobbying spending this year, according to its recent Congressional disclosure forms, which also revealed a major downward revision of the company’s first-quarter expenditures.

BP, whose exploded rig in the Gulf of Mexico caused a multi-month spill, reported spending $3.32 million to lobby in the first half of this year, about 43 percent of what it shelled out in the first six months of 2009.

The new filings show that BP spent $1.72 million in this year’s second quarter, which included the beginning of the April 20 spill. By comparison, the company spent $4 million in the second quarter of last year.

BP’s five-page lobbying report filed Tuesday evening includes only one reference to issues related to what it called “the Gulf of Mexico incident” — an environmental catastrophe that has spurred efforts by lawmakers and the White House to tighten oversight of offshore drilling operations.

While BP officials have devoted a considerable amount of time to testifying on Capitol Hill since the spill, preparation for such testimony is not considered a reportable lobbying expense.

BP’s Washington, D.C., office also filed late Tuesday an amendment to its first-quarter report revising its spending for those three months from $3.5 million to $1.6 million. The amended filing shows the substantially lower figure, but the originally filed and amended forms appear to be almost identical, including the same number of lobbyists employed and issues covered.

Based on the amended numbers, BP’s lobbying spending for 2010 is the lowest since 2007.

BP spokesman Scott Dean said the downward revision was attributable to a change in the reportable dues the company paid to the America Petroleum Institute, Big Oil’s lobbying organization. He said that prior to this year, API used a more expansive IRS definition of lobbying that included grass-roots and state-level lobbying. The switch to the more narrow lobbying definition, Dean said, “has resulted in a substantial reduction of BP’s reportable lobbying expenditures.”

However, other oil interests, including API, have reported large increases in their lobbying budgets since the BP spill.

API doubled its lobbying tab in the second quarter to $2.31 million. Shell Oil, which is seeking permits to drill off the coast of Alaska, spent $4 million on lobbying in the second quarter, up from $2.27 million in the first three months of 2010.

BP’s filings also show it increased payments to outside lobbying firms in the second quarter to $430,000 from $300,000 in the first three months of the year.

The company paid a total of seven outside firms in each quarter. BP dropped one firm, Arnold & Porter, after the first quarter but picked up another, the Eris Group.

In the second quarter, BP doubled its payments to the Podesta Group and the Alpine Group to $120,000 from $60,000 in the first quarter. It also paid the Duberstein Group $100,000 in both the first and second quarters.

Despite this increased outside spending on lobbying, the company overall reported spending only $120,000 more during the second quarter after the spill than it did the first quarter — an increase of less than 7 percent.