AUSTIN — As pressure mounted for political activist Michael Quinn Sullivan to release the secret recording of his meeting with the Texas House speaker, in which he alleges the politician offered him an illegal quid pro quo, Sullivan said Monday he had turned it over to the Texas Rangers.

In an email obtained by The Dallas Morning News, Sullivan writes to the House Republican Caucus chairwoman, Rep. Stephanie Klick of Fort Worth: "I have made the recording available to the Texas Rangers at their request as part of an ongoing criminal investigation."

The Department of Public Safety, which oversees the Rangers, could not be reached for comment late Monday.

The Rangers are investigating a June 12 meeting of Sullivan, House Speaker Dennis Bonnen and Rep. Dustin Burrows of Lubbock, in which Sullivan alleges the lawmakers offered writers for his website, Texas Scorecard, media credentials if he and his affiliated political group, Empower Texans, refrained from criticizing the legislative session and targeted a list of 10 Republican incumbents. Sullivan secretly recorded the meeting and has let a select group of people listen to the audio.

Bonnen and Burrows have denied the allegations. The production of the recording to the Rangers does not mean it will be imminently released to the public.

But the release of the recording to the law enforcement agency comes at a time when calls are growing for Sullivan to release it publicly.

Earlier in the day, Klick, who took the helm of the House GOP Caucus earlier this month, issued a joint statement on Twitter with Reps. Dan Huberty of Humble, Craig Goldman of Fort Worth and Scott Sanford of McKinney. Together, the four lawmakers make up the caucus' executive committee.

"We call for the complete and unedited public release of the secretly recorded conversation between Speaker Bonnen, Representative Burrows and Michael Quinn Sullivan," the statement said.

Bonnen and Burrows, who resigned his position as caucus chairman after Sullivan's allegations caused an uproar, have denied Sullivan's account of the meeting and called for the release of the recording. Sullivan has threatened to release it publicly but had not done so as of Monday night.

Sullivan did not respond to a request for comment. In his email to Klick, he said: "I have done my part. The burden now is on members of the Caucus, who should compel Speaker Bonnen to retract his false claims against me, a private citizen invited into a meeting he constructed to offer a quid pro quo deal I did not invite or want."

But the conservative firebrand is under growing pressure to make the audio public.

Last week, Lt. Gov. Dan Patrick, the state's second-highest public official, said the recording should be released. "Let the public hear it," Patrick, who has received political donations from Empower Texans, told the conservative talk show host Mark Davis. "That's my sense of it. Transparency is important in these things."

Gov. Greg Abbott has called for a swift resolution to the issue, though it appears he hasn't commented on whether the recording should be released.

Top Democrats, such as House Democratic Caucus Chairman Chris Turner of Grand Prairie and Speaker Pro Tem Joe Moody of El Paso, also have urged for the recording to be made public. In a lawsuit that alleges election law violations occurred at the June 12 meeting, the Texas Democratic Party has asked for the recording to be turned over as evidence.

Republican lawmakers, activists and political consultants also have clamored for release. Most recently, Flower Mound GOP Rep. Tan Parker, who immediately preceded Burrows as caucus chairman, joined the calls. Parker was one of the 10 lawmakers whom Bonnen and Burrows allegedly targeted.

"We have had enough lies, half-truths, and political spin, and the people of Texas deserve better," Parker said in a written statement on Monday. "My hope is that everyone will hear this audio recording and know the truth."

But the pressure is also growing on Bonnen and Burrows to clear up what happened in the meeting. Parker, who has heard Sullivan's recording, was critical of Burrows' recent media interviews — his first public comments since the allegations — in which he said "nothing illegal" happened during the rendezvous and that the primary purpose was to keep a Republican majority in the House.

"Our Party and grassroots would be much better served if both the Speaker and Dustin Burrows would be honest and more forthcoming on what really transpired," Parker said. "The recording is only one source of truth, and they have the duty to be the other. Sadly, that hasn't happened again over the past few days through the media interviews with Dustin Burrows."

On Friday, Parker also signed onto a letter from 30 members of the House Republican Caucus calling for the upcoming election of a caucus vice chairman to be held in person. The caucus must elect a new vice chairman because Klick vacated the position when she filled Burrows' position following his resignation. But the meeting request, which was signed by all 10 of the lawmakers who were allegedly targeted, was also seen as a vehicle to discuss the meeting as a caucus.

On Monday, the caucus' executive committee denied the request for that meeting. Instead, the committee called a caucus meeting for Oct. 18, during the group's previously scheduled retreat.