Newark Mayor Cory Booker speaks with a reporter at the Newark City Hall on May 8, 2013. (John Moore/Getty Images)

Newark Mayor and U.S. Senate candidate Cory Booker is accused of mismanaging a large grant to his New Jersey city's school system in an ad released Thursday by a conservative political group. The charge is vigorously denied by Booker's staff.

"This laughable and deeply misleading ad denigrates the efforts of thousands of people who work hard every day to improve Newark's public schools," said Kevin Griffis, a spokesman for the Democratic mayor's Senate campaign, in an emailed statement to U.S. News.

The ad, released online by the American Commitment Action Fund, implies the $100 million donated by Facebook CEO Mark Zuckerberg to the school system hasn't made anything better for students.

The enormous grant was announced on Oprah Winfrey's TV show in September 2010. Winfrey is hosting a fundraiser for Booker's Senate campaign Thursday evening in Jersey City – with tickets starting at $1,000, according to the Sunlight Foundation.

Debate surrounding the donation isn't new. The state chapter of the American Civil Liberties Union filed a lawsuit in 2011 seeking emails between Facebook representatives and Newark officials about the funds.

A judge ordered the emails be released in December. "[Zuckerberg's] money is not going in to classrooms," Booker aide Sharon Macklin said in one of the messages, The Wall Street Journal reported.

"A mayoral adviser outlined a rough plan to spend $315,000 on efforts such as polling, focus groups, mailing and consultants," the Journal reported, citing the emails. "The [Foundation for Newark's Future] has spent at least $2 million on such efforts since."

Around $50 million of the donation reportedly went to a new teachers contract - adopted in November 2012 - that featured merit-based pay increases, and additional funds are reportedly going to open new charter schools.

Booker's campaign points to the teachers contract as one highly significant and positive change for students.

"The giving Mayor Booker has attracted is making a difference in the lives of Newark's children, and the evidence is everywhere," Griffis wrote. "From funding in the breakthrough teacher's contract that rewards great teaching to longer school days to a 61 percent increase in pre-schoolers in district classrooms to the launch of an innovation fund that supports teachers who have new ideas for enriching classroom learning."

A voicemail left with the group behind the ad was not immediately returned. The group's website says it is "committed to defeating big government liberals and electing free-market conservatives" and that targeting Booker is its first project.