On Thursday, BP and its major contractor, Transocean, traded terse letters laced with accusations of corporate irresponsibility – letters that quickly and seemingly strategically made their way into the press.

First, it was Transocean to BP. Steven Roberts, a top corporate counsel for Transocean, said BP was withholding a slew of documents it needed for its internal investigation.

And by day’s end, BP’s James Neath fired back, sending Roberts a note saying the Transocean letter was nothing more than a “publicity stunt evidently designed to draw attention away from Transocean’s potential role in the Deepwater Horizon tragedy.”

BP said it “certainly is not ‘withholding evidence’ ” – as Transocean claimed, Neath wrote in the letter obtained by POLITICO.

The London-based energy company rebuffed Transocean’s main claim, saying it has provided investigatory bodies with documents necessary to investigate the disaster, which killed 11 offshore workers and spilled millions of barrels of oil into the Gulf. BP also said it has provided thousands of documents to Transocean and will provide all of the 16 sets of documents it requested in its latest letter. In fact, Neath wrote, Transocean is withholding information from BP

BP challenged Transocean to do as it has done and make the results of its internal investigation public as well.

A Transocean spokesman was not immediately available for comment.

The tit-for-tat has been a common thread since the massive oil spill in the Gulf last spring. The two companies – along with Halliburton, which also did work on the runaway well – went back and forth on who was to blame during congressional testimony in the weeks following the disaster.

In its letter Thursday, Roberts charged that BP has ignored repeated requests for documents related to the explosion and sinking of the Deepwater Horizon oil rig in the Gulf, leaving Transocean unable to conduct its own investigation.

In a terse seven-page letter to BP’s managing attorney and its associate general counsel, Roberts accused the company of ignoring at least seven requests for information. These documents include logs, cementing and operational reports and seismic data that Transocean believes are keys in its own investigation of the disaster.

“We are unable to understand BP’s continued refusal to provide documents in response to our outstanding requests — documents that only BP has and that are critical to an honest assessment of the incident and the identification of possible improvements for the entire industry,” Roberts wrote in the letter, also obtained by POLITICO.

The letter was also sent to Energy Secretary Steven Chu, Coast Guard Capt. Hung Nguyen, Interior Secretary Ken Salazar, House Energy and Commerce Committee Chairman Henry Waxman (D-Calif.), Reps. Joe Barton (R-Texas), Ed Markey (D-Mass.), Bart Stupak (D-Mich.), House Natural Resources Committee Chairman Nick Rahall (D-W.Va.), Senate Environment and Public Works Committee Chairwoman Barbara Boxer (D-Calif.), Sen. Jim Inhofe (R-Okla.), Senate Energy and Natural Resources Committee Chairman Jeff Bingaman (D-N.M.), Sen. Lisa Murkowski (R-Alaska), Attorney General Eric Holder and the co-chairmen of the commission investigating the disaster.

Responding, BP said in a statement that it had reviewed Transocean’s letter and would answer it “promptly.”

“We are disappointed that Transocean has opted to write a letter with so many misguided and misleading assertions, including the assertion that BP is ‘withholding evidence’ concerning the April 20th accident and the resulting oil spill,” BP’s statement went on. “We have been at the forefront of cooperating with various investigations commissioned by the U. S. government and others into the causes of the Deepwater Horizon tragedy. Our commitment to cooperate with these investigations has been and remains unequivocal and steadfast.”

Transocean, though, also believes that BP has not given the information to government investigative bodies.

“Many of these documents are integral to the design and construction of the Macondo well and, therefore, to its ultimate failure,” a Transocean spokesman told POLITICO.

BP has produced “some documents,” Transocean says, but no records since June 21. And Swiss-based Transocean says BP hasn’t acknowledged receipt of a letter since Aug. 3.

Transocean is seeking 16 different sets of records, including blowout preventer test results, lab reports, details about the well casing, drilling mud reports, gas composition and flow rate data and a BP organizational chart, among other things.

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

The legal spat is likely to cause ire on Capitol Hill as well. Markey, who chairs a House energy subcommittee, has lashed out at BP for providing misleading flow rate information to congressional investigators. And Stupak and Waxman have been staunch in their insistence that BP to be transparent and forthcoming with information.

“Transocean has continued its requests to BP to be open and transparent, with the hope that BP shared our commitment to allowing everyone to discover the truth and to make improvements for the entire industry,” Roberts wrote in his letter.