A group of Texas pastors is filing charges against Houston Mayor Annise Parker for allegedly violating their religious freedom after they were subpoenaed last year for speaking out against the mayor, homosexuality, or anything regarding the Houston "Bathroom Bill."

Last year, Parker—the first openly lesbian mayor of a major US city—pushed for the passage of the "Equal Rights Ordinance" which was designed to neutralise any form of discrimination in Texas, including "gender identity," according to Christian News.

However, the "Public Accommodations" section of the ordinance raised public concerns since it would allow men to use women's restrooms, and vice versa, depending on their gender association.

"It shall be unlawful for any place of public accommodation or any employee or agent thereof to intentionally deny any person entry to any restroom, shower room, or similar facility if that facility is consistent with and appropriate to that person's expression of gender identity," the ordinance states.

Several individuals and pastors then worked together to repeal the ordinance, collecting over 55,000 signatures seeking to oppose it. City Secretary Anna Russell confirmed in writing that 17,846 signatures were already acceptable, since the minimum required by the city for a referendum is 17,269. However, it was rejected by Parker and the city attorney.

In August 2014, those behind the initiative filed a lawsuit against Parker for rejecting the signatures and the referendum. In turn, Houston's attorneys subpoenaed several of the pastors involved, demanding that they stop "all speeches, presentations, or sermons related to (the ordinance), the petition, Mayor Annise Parker, homosexuality, or gender identity."

Now, the subpoenaed pastors are filing a suit against Parker for "trampling on the rights of one million Houston citizens." Plaintiffs include F.N. Williams, Sr., of Antioch Missionary Baptist Church; Hernan Castano, director of Hispanic Church Development for the Houston Area Pastor Council; Magda Hermida of Magda Hermida Ministries; and Khanh Huynh of Vietnamese Baptist Church.

Late last month, the Texas Supreme Court ruled that officials must either repeal the ordinance by Aug. 24, or place the measure on the November ballot.

However, the ordinance is unlikely to be repealed since the majority of Houston's council members support it.

Parker expressed her "disappointment" with the court's decision, saying she believes the high court is "in error."

"We will proceed with the steps necessary for city council to consider the issue," she said. "At the same time, we are consulting with our outside counsel on any possible available legal actions."

The ordinance, which was passed in May 2014, has been debated for months, as the new regulations allow transgenders to file complaints if they are denied restroom usage and discriminated against in both business and housing.