WASHINGTON (AP) _ It cost Atlantic Richfield Co. $42,000 to send House Speaker Newt Gingrich, his wife and two aides on a five-day trip to London in December for a private speech to oil company executives and their guests.

Gingrich, R-Ga., disclosed the expenses as required under new House rules, which permit lawmakers to be reimbursed by special interests for travel associated with their official duties.

The speaker's trip is among the most expensive disclosed so far under the two-year-old rules. It included first-class air fare, limousine transportation while in London, and lodging at the exclusive hotel Claridge's.

During the trip, Gingrich also met with British Prime Minister Tony Blair and other political leaders, spoke publicly at London University and toured the Museum of Natural History, the zoo and Westminster Abbey.

While in London, Gingrich, R-Ga., also met privately with Arco Chairman Michael Bowlin, mostly as preparation for his dinner speech, said Christina Martin, Gingrich's spokeswoman.

By far the biggest item on the speaker's travel tab was transportation. Air fare and ground transportation for Gingrich and his wife Marianne cost $20,268. Separate transportation for the two aides totaled $3,300.

The stay at Claridge's for the speaker and his wife cost $12,225; for each of the aides, it averaged about $2,500. Meals for the group totaled $947.

Martin said the House ethics committee approved the trip in advance, and she defended it by saying it cost ``less than a 90-minute flight aboard Air Force One,'' the presidential jet.

An Arco spokesman, Al Greenstein, said the company has sponsored the dinner every year since 1976, seeking speakers ``whose views are of interest to an audience of government and business leaders of the United Kingdom'' and top Arco executives.

Previous dinner speakers include former presidents Reagan, Bush and Carter, retired Gen. Colin Powell and former Senate Majority Leader Bob Dole, R-Kan. Only Dole and Gingrich were in office at the time of their speeches.

Rules that took effect two years ago banned most special-interest gift-giving to members of Congress, but left one large exception: all-expense-paid travel. The rules require only that the trips be connected with a lawmaker's official duties and be disclosed within 30 days. First-class travel and luxury accommodations are allowed as ``reasonable'' expenses _ an interpretation critics say is a loophole for undue influence by wealthy interests.

Prior to the new rules, special interests often sponsored lawmakers' trips, but costs and details were not disclosed.

An Associated Press analysis of 1996 records showed various interests picked up the tab for $4.6 million in trips that year for members of Congress and their staffs. The most expensive trip in 1996 was a $16,000, 10-day journey to Africa by then-Rep. Jack Fields, R-Texas. A trip to the Middle East last year by Sen. Robert Torricelli, D-N.J., and two aides cost $27,000.

Arco is among companies seeking to develop oil resources in the environmentally sensitive Arctic National Wildlife Refuge; it has sponsored travel for congressional aides to the area to boost its arguments for drilling.