LONDON (Bloomberg)—BP P.L.C. fired back at Transocean Ltd. in a dispute over the withholding of information about possible causes of the Gulf oil spill.

James Neath, BP's associate general counsel, said a Wednesday letter from a Transocean attorney asserting BP wasn't releasing critical data contained “many false and misleading assertions.”

“Given its content and tone, your letter is nothing more than a publicity stunt evidently designed to draw attention away from Transocean's potential role in the Deepwater Horizon tragedy,” Mr. Neath wrote Steven Roberts, the Transocean attorney, in a response Thursday.

Executives of London-based BP and Vernier, Switzerland-based Transocean have publicly disputed responsibilities for operations of the BP well and the Deepwater Horizon drilling rig that it leased from Transocean. The companies engaged in finger-pointing before Congress over steps that may have contributed to the April 20 explosion that killed 11 workers and triggered the largest U.S. oil spill.

Transocean said in its letter that BP's “continued refusal to provide documents” was blocking efforts to determine the cause of the spill.

BP hasn't provided documents requested by Transocean since June 21, Mr. Roberts said in the letter sent to BP and copied to officials in the Obama administration and members of Congress.

Mr. Neath said that BP made available on July 16 more than 100,000 pages of documents to Transocean “for access, download and review.” Mr. Neath copied his letter to the same administration officials and lawmakers.

220,000 pages

The database has grown to more than 220,000 pages of documents since then, including some of the categories of information that Transocean accused BP of withholding, Mr. Neath said in the letter.

Members of Congress and the U.S. Joint Investigation Team's Marine Board of Investigation, one of several federal panels that are investigating the spill, also have had access to the database, Mr. Neath said.

“Our commitment to cooperate with these investigations has been and remains unequivocal and steadfast,” Mr. Neath said.

Rep. Bart Stupak, D-Mich., chairman of the House Energy Committee's investigations panel, said Thursday that “it has been, at times, challenging to obtain complete information from BP.”

“The companies involved with the Deepwater Horizon, including BP, should be sharing information so regulators as well as the industry as a whole can understand what went wrong and how to prevent it in the future,” Rep. Stupak said in an e-mailed statement.

Blowout preventer

Transocean's letter lists outstanding requests to BP for 16 categories of information, including details on digital pressure tests on the blowout preventer, a last line of defense against an uncontrolled spill. The device failed to seal BP's ruptured Macondo well.

“BP has in its sole possession a significant amount of key information about the well,” Mr. Roberts said.

Without access to the information, “the task of fairly determining the cause and measures to improve the safety of all offshore workers cannot be completed in a manner that instills confidence in any findings,” Mr. Roberts said.

The letter also accuses BP of withholding information on the process the company used to close previously drilled wells, tests on cement used to seal the Macondo well and an organizational chart establishing a chain of command at BP.

Mr. Neath wrote back that some of the information “concern data and reports that are or should be in the possession of third parties,” including Halliburton Co., which provided cement for the well.

‘Ridiculous spectacle’

The letters continue a pattern of finger-pointing since the explosion.

Lamar McKay, chairman of BP America Inc., told a Senate Energy Committee hearing on May 11 that “Transocean’s blowout preventer failed to operate.”

Steven Newman, Transocean’s CEO, told the same panel that “all offshore oil and gas production projects begin and end with the operator.”

President Barack Obama on May 14 criticized the “ridiculous spectacle” of finger-pointing among BP, Transocean and Halliburton.

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