Texas investigators are defending their decision to employ some of Google’s longtime foes as part of an antitrust probe into the search giant, saying in a court filing that the recent legal objections raised by the company threaten to “severely compromise” states’ scrutiny.

At issue are a number of consultants retained by Texas Attorney General Ken Paxton, who is leading an inquiry into Google’s ad business that’s backed by 50 other attorneys general. The experts include people who previously have worked on behalf of Google’s rivals, including News Corp., in antitrust battles around the world.

In October, Google lawyers asked a Texas court to limit those consultants’ access to the tech giant’s secrets. Almost two months later, Texas officials told a judge in Travis County that Google’s requests are highly problematic, serving only to try to block much-needed experts from contributing in a complicated matter. The Washington Post obtained the documents, dated Dec. 9, through an open-records request.

“Google’s Petition, under the guise of protecting confidential information, seeks to frustrate the [Office of the Attorney General's] statutorily-prescribed investigative authority by severely hampering the [office's] lawful ability to employ the services of experts, consultants, and others for purposes of the investigation,” lawyers for Texas argued in their filing.

In response, Google spokesman Jose Castaneda in a statement described the attorney general's hires as an “extraordinarily irregular arrangement,” adding it is “only fair to have assurances that our confidential business information won’t be shared with competitors or vocal complainants."

The back-and-forth between Texas and Google reflects the high stakes in what’s likely to be a long, sweeping antitrust review of Google’s business practices. The probe, announced in September, is focused on Google’s online-advertising operation, which helped generate $117 billion for the company last year. Paxton and his Democratic and Republican colleagues are probing whether Google’s ad practices harm a wide array of businesses, including news publishers, and result in higher prices, worse service or fewer choices for consumers online.

The states’ effort is one of several major antitrust probes into Google in the United States and around the world: In Washington, the Justice Department similarly is scrutinizing the company, while House lawmakers have pored over Google records as part of a review of big tech and federal competition laws. Abroad, competition watchdogs in the United Kingdom have opened their own review into Facebook and Google. On Wednesday, they issued an interim report finding the companies “may have become entrenched with negative consequences for the people and businesses who use these services every day.”

In response, Google has defended its practices on each of those fronts, claiming it has actually created competition, not limited it. But the company has taken special exception with Texas and Paxton in response to two experts the Lone Star State tapped this year to study the matter.

The first, Cristina Caffarra, is a top competition expert at Charles River Associates, where she has represented clients including the Rupert Murdoch-backed News Corp., which previously has called for a breakup of Google. Caffarra has been most active in Europe, where regulators have repeatedly fined Google for violating competition laws.

The second expert, Eugene Burrus, has been behind lawsuits and investigations into Google’s business practices, the tech giant contended in its October filing. Much like Caffarra, Google has expressed concerns with his selection, including fears he could take the knowledge gleaned from the Texas probe and battle the tech giant again in the future.

In October, Google urged a judge to impose an order on Caffarra, Burrus and others from disclosing certain information or working for any of Google’s rivals for a year after the probe concludes.

In their response, Paxton’s team argued it had already sought to protect Google’s confidential information. The attorney general’s team said its contracts “expressly provide that any information obtained via the investigation is not to be shared with any third party or used for any purpose other than the investigation."

The order that Google proposed, however, would be “so expansive that it would severely compromise the [office’s] ability to hire an expert, court reporter, or even graphic support for this investigation,” Paxton’s lawyers said.

And Texas charged that Google essentially would “gate an investigative process which is, by its nature, fluid depending on the evidence that is uncovered.” In doing so, Texas offered the latest indication that the 51 attorneys general involved in the investigation could easily expand their focus well beyond advertising.

“As the subject matter of the investigation is initially broad (Google’s potentially anticompetitive conduct), the specific behavior and acts at issue will likely change and evolve as the investigation progresses,” lawyers for Paxton wrote.