Opponents of the Ground Zero mosque are turning to the courts in a last-ditch effort to block the project that has inspired a national debate and even brought tears to the mayor’s eyes as he defended religious freedom.

Critics lost their last viable chance to derail the $100 million Islamic center Tuesday when the city Landmarks Preservation Commission voted unanimously against preserving a 152-year-old factory building at 45-47 Park Place that will be torn down to make way for the $100 million Islamic community center, called the Cordoba House.

“I’ve spent a lot of time thinking about this case,” said Frederick Bland, a commissioner, before the 9-0 vote at a Pace University auditorium. “Although it’s a handsome (building), it doest not really stand out.”

The vote drew heckles and outcries of “shame” from a handful of critics, one who held a sign saying “don’t glorify murders of 3,000.”

“I think it’s the most insensitive thing that I’ve every heard,” said Tracy Rose, a Upper East Side resident who lost 43 colleagues in the 9/11 attacks. “It’s just wrong.”

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The American Center for Law & Justice, a conservative nonprofit, will file a lawsuit in New York Supreme Court today accusing the commission of letting politics steer its vote, a spokesman said. Still, Mayor Bloomberg and dozens other city officials are backing the center, which will include a performing arts center and other public space.

“We would betray our values - and play into our enemies’ hands - if we were to treat Muslims differently than anyone else,” said Bloomberg, who grew uncharacteristically emotional during his speech Tuesday.

There are no more public hearings on the project, which has generated national attention from Sarah Palin and other conservatives. Construction will take years, as backers still have to raise money and get permits in place.

“I’m ecstatic,” said Dalia Mahmoud, an Upper West Side resident who attended the hearing in support of the mosque. “The majority of New Yorkers are behind this.”