At least two dozen lawmakers own investments in the three companies tied to the Gulf of Mexico oil spill as Congress investigates the disaster and considers reforms.

Lawmakers own amounts ranging from $1,000 to $150,000 worth of BP PLC, Transocean Ltd. or Halliburton Co. stocks and bonds, according to their personal financial disclosures. Several of these lawmakers sit on a committee examining the spill and what changes might be needed to prevent another.

The forms reflect investments in 2008, the most recent information currently available. In several cases, aides confirmed that lawmakers still own the shares.

"This is a serious conflict of interest," said Craig Holman, government affairs lobbyist for Public Citizen, a watchdog group. "Only Congress exempts [itself] from this type of conflict of interest.

"They should not be making decisions that affect their own personal wellbeing," Holman added.

Senate and House ethics rules allow the stock holdings. With very narrow exceptions, lawmakers can invest in companies that could be affected by congressional action. The ethics rules are built on the concept that sufficient public disclosure prevents conflicts, said Robert Walker, counsel at Wiley Rein LLP law firm and former chief counsel and staff director of the both the Senate and House Ethics committees.

"The standard that requires recusal [from involvement in an action] is extremely high," Walker said. "Members may be free to judge what they consider an appearance of a conflict."

Unlike executive branch employees who tend to focus on one area and must recuse themselves when they have a conflict, Congress legislates on potentially everything and members would have to either eschew buying stock or frequently miss votes, Walker said.

In at least one case involving the three oil spill companies, a lawmaker felt that his stock ownership presented a conflict.

Rep. Gary Miller, (R-Calif.), opted out of recent actions involving drilling rig owner Transocean because he who owns $15,000 to $50,000 in company shares. (The disclosures provide only ranges of assets.) Miller did not attend two Transportation and Infrastructure Committee hearings on the oil spill, one on May 19 and the other June 9, according to his spokeswoman, Jessica Baker.

"To further prevent conflict of interest, he did not vote on S. 3473, which would amend the Oil Pollution Act of 1990 to authorize advances from Oil Spill Liability Trust Fund for the Deepwater Horizon oil spill," Baker said. "Congressman Miller will continue to recuse himself from any committee activity regarding the oil spill."

Others, however, rejected the idea that recusal was automatically necessary. Rep. James Sensenbrenner, (R-Wis.) reported holding $144,520 worth of BP shares in his financial disclosure and sits on the House Judiciary Committee, which is examining whether liability limits and favorable court decisions encouraged oil companies to take inappropriate risks.

"At this time, the congressman will not recuse himself, because there is no legislation in front of the House to recuse himself from," said Sensenbrenner spokeswoman Wendy Riemann. "Should an issue arise where there would be a severe conflict of interest between the congressman's finances and legislation, the congressman would weigh his options at that time."

Riemann noted that "no one was telling the congressman he needed to recuse himself when he voted against BP on drilling in ANWR or when he voted against BP on drilling in the Great Lakes or when he voted against BP by voting against the cap-and-trade legislation."

Sensenbrenner, the former chairman of the Judiciary and Science committees, is currently the ranking member of the Select Committee on Energy Independence and Global Warming.

BP ownership

BP leased the Transocean drilling rig, called Deepwater Horizon, which exploded and sank in the Gulf of Mexico on April 20. The well that has been spewing oil since is owned by BP. Halliburton provided drilling on Deepwater Horizon.

Sensenbrenner's stock in BP represented the highest value of the lawmakers invested in the company. However, the $144,520 value he reported is not the current worth of his stock. BP's price has tumbled as much as 40 percent post-spill. Sensenbrenner is one of the few members who reports precisely what he owns instead of the wide value bands used on the forms.

Reimann said Sensenbrenner inherited the stock in 1978 when it was AMOCO, adding, "BP later bought AMOCO, however, the congressman has not touched the stock since he acquired it more than 30 years ago."

How someone acquired his stock is irrelevant, said Tyson Slocum, director of the energy project at Public Citizen. "A source of income is a source of income regardless of whether you inherited it," he said.

Among lawmakers who own BP, those holding some of the largest amounts are Rep. Fred Upton, (R-Mich.), who listed a value range between $16,002 to $60,000 for his shares, and Rep. Mike Castle (R-Del.) who owned between $3,003 and $45,000.

Upton sits on the House Energy and Commerce Committee. In his most recent disclosure form filed last month, but not yet public, he reported that his wife held BP stock valued between $1,001-$15,000 "that she inherited when her mother passed away," said Upton's spokesman Sean Bonyun. He added that Upton has BP holdings valued between $15,001-$50,000 that are part of family trusts.

"Fred has zero control over the holdings in his family trusts or his wife's holdings," Bonyun added.

Bonyun said that Upton has acted against BP's interests "as they sought to increase discharge into Lake Michigan at their Whiting Refinery," and "also taking them on for violating clean air standards." As well, Bonyun said, Upton has "stated repeatedly that it will be BP and not taxpayers who will be on the hook for the cost of the cleanup."

Castle's investments are managed by an adviser, and Castle has no role in buying and selling, said spokeswoman Kate Dickens. The BP stock was scheduled to be sold, she said but it was not clear whether that had yet happened. Castle is running for the open Senate seat from Delaware.

Multiple interests

A few of the House and Senate lawmakers hold stock in more than one of the three companies involved in the spill.

Rep. Kenny Marchant (R-Texas) reported owning $151,625 worth of Transocean, $36,360 of Halliburton, and $8,646 of BP. Marchant's office did not respond to several requests for comment.

Sen. John Kerry (D-Mass) disclosed owning $65,002 to $150,000 worth of Transocean and $1,001 to $15,000 in BP stock. That amount is the highest value reported for shares of Transocean.

Kerry is sponsor of climate legislation along with Sen. Joe Lieberman (I-Conn.) and is of the wealthiest members of Congress, with an extensive portfolio of investments.

"Senator Kerry has been the Senate's best environmental champion for more than 25 years and has written and urged legislation to end our dependence on foreign oil," said his spokeswoman Whitney Smith. "Inherited holdings in family trusts he has no control over whatsoever clearly have no impact on his fight for a green economy and a clean environment. Indeed, by that standard, he's cast scores of votes against his own economic interests, and these industries have spent millions against him in political and legislative campaigns."

Rep. Michael McCaul (R-Texas) reported holding stock valued at $1,001 to $15,000 each for both BP and Transocean. "He is not involved in decisions regarding his personal investments and has no detailed knowledge of them," said McCaul spokesman Mike Rosen.

Asked about McCaul's position on oil drilling, Rosen said that "Representative McCaul has consistently supported an 'all of the above' energy policy which balances increased oil and gas exploration with the advancement of alternative fuels." McCaul also has supported alternative energy legislation, Rosen said.

Rep. Jerry Moran, (R-Kan.) said in his disclosure that he owned $15,001 to $50,000 in Transocean shares and $1,001 to $15,000 in Halliburton. His office did not respond to several requests for comment, and it was not possible to know whether he still owns the stocks.

Holding Halliburton

Sen. Kay Bailey Hutchison (R-Texas) owns $15,001 to $50,000 in Halliburton according to her report, the highest value of Halliburton shares among the lawmakers. Her spokeswoman Courtney Sanders would not say whether Hutchison still owns the stock.

"Senator Hutchison has always fully disclosed her financial holdings in compliance with Senate ethics rules," Sanders said.

Hutchison recently opposed President Obama's move to freeze expansion of offshore oil drilling. "This devastating but isolated incident must not result in an end to offshore energy exploration and development," Hutchison said in a June 4 statement. "Oil and gas remain a critical part of a balanced domestic energy portfolio."