WASHINGTON — The U.S. House of Representatives on Tuesday passed a financial deregulation package that would benefit the Koch brothers and the nation’s largest banks by a vote of 265-143.

The legislation would significantly weaken elements of the 2010 Dodd-Frank financial reform law dealing with derivatives — the complex products at the heart of the 2008 meltdown. Many components of the bill approved Tuesday had previously passed the House with bipartisan support. However, Democratic backing had been weakest on the most controversial measure, which allows U.S. firms to skirt domestic regulations on some derivatives by conducting trades through offshore affiliates in other major financial centers.

Republicans were almost uniform in their support, with Rep. Walter Jones (N.C.) the lone GOP holdout. Democratic opposition was broad, with only 46 Democrats voting in support — a marked change from several recent House votes on Wall Street deregulation that have drawn substantial backing from dozens, and in some cases an overwhelming majority, of House Democrats. The White House issued a formal statement last week saying that it “strongly opposes” the legislation that passed Tuesday.

The bill includes several separate deregulatory measures sought by the largest Wall Street banks and the Koch brothers, who control significant financial and energy derivatives operations. Americans for Financial Reform, the premier policy analysis organization among bank watchdogs, advocated strongly against the bill alongside consumer groups and the AFL-CIO.

The bill also reauthorizes the existence of the primary derivatives regulator, the Commodity Futures Trading Commission. Bank reform advocates, however, are confident that the agency cannot be shut down, unless it’s defunded by Congress. The CFTC’s formal authorization expired in October 2013.

The Democratic Party has been roiled in recent months by internal divisions over its relationship with Wall Street, with one wing of the party attempting to cozy up to financiers in pursuit of campaign cash and another seeking to rein in banking excess. In Congress, the turmoil has divided even traditionally progressive organizations, including the Congressional Black Caucus. The CBC largely opposed the CFTC bill Tuesday, with only Reps. G.K. Butterfield (D-N.C.) and David Scott (D-Ga.) voting for it. Twenty-five members of the corporate-friendly New Democrat Coalition voted for the bill.

The offshoring provision of the bill is derided as the “London Whale Loophole Act” by its critics, a reference to JPMorgan’s infamous trade conducted out of its London office that cost the bank over $6.2 billion in abrupt losses. The provision received 73 Democratic votes on the floor last year and had two Democratic co-sponsors, Scott and Rep. John Carney (Del.). Both have frequently backed Wall Street deregulatory measures. Reps. Jim Himes (D-Conn.) and Gwen Moore (D-Wis.), who have also been sympathetic to Wall Street, co-sponsored a similar bill in 2011. Himes, Moore and Carney all voted against today’s bill.

Other deregulatory provisions in the bill had previously passed the House in bipartisan blowouts, with one clearing 423-0 and another 441-12. Some of the provisions in the bill voted on Tuesday are now largely symbolic, as they have already influenced CFTC rules.

But the Democrat-controlled Senate has not taken up the various deregulatory measures, most of which first cleared the House separately more than a year ago. By lumping the measures together, deregulation supporters had hoped to generate broader support to pressure the Senate into action, an unlikely prospect after Tuesday’s vote.

Tuesday’s bill would also require the CFTC to conduct extensive cost-benefit analyses for a host of derivatives regulations. The GOP has insisted that such analyses will improve efficiency, but bank watchdogs view them as an effort to hamstring ordinary oversight. Quantifying the long-term costs and benefits of a rule is effectively impossible when the risks include financial panics and their aftermath. Many traditional regulations on food safety and other measures have been considered critical to the public good irrespective of their cost. Both Moore and Financial Services ranking Democrat Maxine Waters (Calif.) introduced amendments that would have curtailed the effects of these analyses, but they were voted down by the GOP.

Republicans on the House Rules Committee had blocked more aggressive oversight amendments from Waters and Rep. Stephen Lynch (D-Mass.), preventing floor votes on them. Lynch’s proposal would have required greater scrutiny of high-frequency trading. Waters’ amendment would have banned anyone who had been convicted of violating securities laws, or who is the subject of a formal ongoing securities law investigation, from serving on the CFTC’s advisory committee.

Former JPMorgan Managing Director Blythe Masters was named to that committee early this year, but quickly resigned the post. In April, reports surfaced that she was being investigated by the FBI over the bank’s commodity trading operations. The company agreed to pay $410 million last year to settle civil allegations of impropriety in Masters’ division.