Cory Booker speaks at the 2013 Greater New York Human Rights Campaign Gala in New York City, Feb. 2, 2013. (Brad Barket/Getty Images)

Newark, N.J., Mayor Cory Booker, the front-runner ahead of the Oct. 16 special election to replace the late Sen. Frank Lautenberg, D-N.J., is being accused of slander and neglect by the Associated Humane Societies, which operates Newark's only animal shelter.

City officials have been planning for five years to open a no-kill animal shelter in Newark to compete with the AHS for city contracts because Booker and other officials disapprove of the number of animals euthanized at the existing facility.

Booker, a rising superstar within the Democratic Party, has built a reputation as an animal lover who has on several occasions personally intervened to take dogs out of bad situations.

But Scott Crawford, the assistant director of AHS, which operates two shelters outside of Newark and a zoo featuring rescued exotic animals, said Booker "never shows up and he never answers our calls."

"He keeps belittling us and causing problems," Crawford said, describing how he heard Booker give local broadcast interviews earlier this year "saying we're the most dirty slaughterhouse in the world," which Crawford calls "negative propaganda."

Two city officials who work closely with Booker agreed to speak with U.S. News about the dispute on the condition that they not be identified. They said the mayor, to their knowledge, has never used the term slaughterhouse.

The two sides disagree on other facts as well. Crawford says the mayor never visits the shelter, but one of the city officials said Booker did indeed visit early in his administration, which began in 2006. The officials also said they have no record of recent attempts by the AHS to contact Booker directly.

Both sides agree that the relationship between the shelter – the largest in New Jersey – and the city government is poor.

The city officials who requested anonymity said the AHS shelter has a "track record of squalor" and "horrific conditions" that are "very sad and troubling." Crawford says such assertions are "slanderous untruthful things." The officials also cited "thousands of savable animals" who were euthanized in recent years.

Crawford expressed sorrow over the deaths, but said the shelter risks the spread of disease with overcrowding and must euthanize animals that are terminally ill, too aggressive to rehabilitate or suffering from advanced age. In some instances – particularly during the summer – "some great pets, at no fault of their own, will be humanely euthanized" because too few people are willing to adopt the stray or abandoned animals, he said.

Annual reports provided by Booker's office show high kill rates. In 2010, the shelter euthanized roughly 35 percent of the 2,471 dogs it took in and nearly 70 percent of the 2,694 cats it housed. In 2011, the shelter euthanized 30 percent of the 2,382 dogs it received and about 72 percent of its 2,563 cats.

In 2012, according to a report provided to U.S. News by the shelter, nearly 13 percent of the 2,210 dogs it received and slightly more than 50 percent of 2,272 cats were killed, a steep decline in the euthanasia rate attributable to an uptick in adoptions. According to the shelter, the rate is on track to drop further in 2013.

"Sadly, people are not knocking down our doors to adopt these poor feline friends of ours," the shelter leader said. "The overall problem of homeless animals in New Jersey is something that people really do not see or understand. A lot of times when an animal dog or cat comes into us it is the first time that they actually are given the feeling of true love and compassion."

Crawford said he wants the city to enact stricter animal cruelty laws, more stringent spay and neuter policies and new regulations to trim down on so-called "back yard" breeders in the inner city.

"All we want is for [Booker] to work with us for what's best for the animals," he said. "Wouldn't he want to work hand in hand with us and come up with ways together to solve his city and this state's unwanted and homeless animal problem, instead of always attacking us and making it that much harder for us to operate our mission?"

One city official characterized Crawford's charges of neglect and slander as "unsubstantiated allegations from a disgruntled organization that has been fighting with us for years."

A female pit bull rescued from an abusive situation by Booker on June 27 added to tensions. The dog is vicious and despite attempts by shelter workers, appears unlikely to be rehabilitated, Crawford said.

"We are here to give every animal a fair chance and by discrediting us or by saying he needs to follow up on this sad girl to ensure we will do the right thing by her (when he never intends to follow up) makes our mission that much harder," Crawford wrote in an email.

Booker's staff says the mayor has exchanged multiple emails with city officials who have checked in on the dog at his request.

In a statement provided to U.S. News, Newark Deputy Mayor Adam Zipkin said, "Due to our extreme dissatisfaction with the level of care at the existing AHS facility – and because far too many of the animals are unnecessarily killed there each year by AHS – we anticipate breaking ground this fall on a new state-of-the-art, no-kill animal shelter in Newark that will provide the highest quality of care for neglected and abused animals."

But the new shelter has been planned for years and Crawford says he doesn't think it will ever open. "I do not fear them opening another shelter," he said. "I just want the city to work with us in being a real cause to the solution to this problem instead of adding it."