HOUSTON -- Opponents of Houston's equal rights ordinance are vowing to keep fighting after the city denied their petition. City officials announced Monday that thousands of pages a petition to take down the HERO ordinance are invalid.

According to the city, many of the pages were circulated by people who don't live in Houston. Opponents gathered almost 52,000 signatures and only needed about 17,000. The city says only 15,249 signatures are valid.

Mayor Annise Parker says that means there will not be a referendum on the November ballot.

"I fully expected it to end up on a ballot and that we would win. If it does not end up on a ballot, it saves the city a significant amount of money," said Parker.

Religious leaders who helped gather signatures say they are disappointed but not surprised by the city's announcement.

"Unfortunately we know who we're dealing with, and we're dealing with a biased administration," said Dave Welch, executive director of Houston Area Pastor Council. "If the mayor's so confident in her position on the vote, give the benefit to voters and let us have a voice."

Welch said he is already planning legal action.

KHOU 11 News legal expert Gerald Treece expects a lawsuit to be filed within two days.

"The question is not will a lawsuit be filed against the city. The question is which group will win the race to the courthouse to file it," said Treece.

Mayor Parker says she was fully expecting the legal fight that lies ahead.

When asked for her personal opinion on the matter, she replied, "It is what it is."