A legal battle between the city of Houston and religious leaders has erupted into a national debate about religious liberty and freedom of speech, even as Mayor Annise Parker argued the controversy was based on a misunderstanding.

Conservative lawmakers and activists expressed outrage upon learning that lawyers acting on behalf of the city had sent subpoenas this month to pastors who had vocally supported a failed petition drive aimed at repealing Houston's equal rights ordinance.

The ordinance, better known by its acronym, HERO, expanded the city's ban on discrimination to include sexual orientation. It applies to businesses that serve the public, as well as city contractors and municipal workers. The City Council approved it in May after an intense public debate.

In August, city officials announced that an effort by conservative activists and pastors to put the ordinance's repeal to voters failed to draw enough signatures. Opponents of the ordinance have since taken the issue to the courts, alleging in a lawsuit that the city inappropriately disqualified some of the signatures.

The subpoenas, sent to some outspoken pastors and religious leaders who had opposed the ordinance, had asked for "all speeches, presentations, or sermons related to HERO, the Petition, Mayor Annise Parker, homosexuality, or gender identity prepared by, delivered by, revised by, or approved by you or in your possession."

Various public officials, including religious liberty advocates, have condemned the subpoenas as censorship and an attack on religious liberty.

"This week, the government of Houston, Texas, sent a subpoena to silence prayers," U.S. Sen. Ted Cruz said Thursday at a news conference in Houston.

Attorney General Greg Abbott sent a letter to Houston City Attorney David Feldman urging him to withdraw the subpoenas.

"No matter what public policy is at stake, government officials must exercise the utmost care when our work touches on religious matters," Abbott wrote. "If we err, it must be on the side of preserving the autonomy of religious institutions and the liberty of religious believers. Your aggressive and invasive subpoenas show no regard for the very serious First Amendment considerations at stake."

State Sen. Ken Paxton, the Republican candidate to replace Abbott as attorney general, called the subpoenas "unacceptable."

"Not only does this infringe upon the right to Freedom of Speech, but it also grossly encroaches upon our Freedom of Religion - both fundamental rights protected by the U.S. Constitution," Paxton said.

Both Parker and Feldman have said that they did not approve the subpoenas ahead of time and first saw the language used in them on Tuesday. The subpoenas were handled by outside lawyers working on behalf of the city. Both agreed that the language in the subpoenas was overly broad and would be clarified.

"We are not interested at all in what some person may have preached about me or the GLBT community," Parker said Wednesday at a news conference. "People are rightly concerned if a government entity tries to in any way inhibit religious speech. That is not the intent."

Parker said the goal of the subpoenas was to see if there were any specific instructions given by pastors about how the petitions should be filled out. She suggested that the outrage over the word "sermon" in the subpoenas may have been due to "deliberate misinterpretation."

"Let me just say that one word in a very long legal document which I know nothing about and would never have read and I'm vilified coast to coast - it's a normal day at the office for me," Parker said.

But Cruz echoed other conservatives Thursday in framing the issue as a severe threat to religious liberty.

"This is a country that was formed centuries ago by people fleeing religious persecution seeking a land where you do not need to seek the permission of a king or queen or president to preach the word of God, because we serve a higher authority," Cruz said.

On Thursday, Cruz tweeted a website purchased a day earlier: standwithpastors.com. Visitors to the site were redirected to a petition on Cruz's campaign website.