New York- A Manhattan madam who has denied hiring underage hookers gave a 15-year-old girl a fake ID and ordered her to “be a thoroughbred” in bed, prosecutors charged yesterday.

Sex-den doyenne Julie Moya, 47, was being held on $500,000 bail last night as cops and FBI agents squeezed her to give up her big-name johns and scoured her computerized client list, sources said.

Moya, who has portrayed herself as a hooker honcho with a heart of gold, was accused yesterday in Manhattan Criminal Court of running brothels where drugs were rampant, and johns were rarely denied their wildest fantasies.

Prosecutor Matthew Bassiur said Moya was “well aware” some of her prostitutes were underage, including a 15-year-old cooperating with investigators.

“The defendant personally supplied a 15-year-old with fake ID saying she was 19,” said Bassiur, alleging Moya told the girl to use the bogus document if any johns questioned her age.

“She told the girl she couldn’t be shy and that she had to be a thoroughbred and do whatever the johns want.”

But in an exclusive interview in Sunday’s Daily News, Moya denied employing underage girls. “There were never any underage girls. Never, never, ever,” she said. “I ask them for IDs and try to make sure they’re of age.”