It's one of the city of Newark's closest held secrets -- what are the details of the bid submitted to Amazon for its new HQ2 headquarters?

Despite the public dollars involved in the bid, those details are being kept under seal.

Over the last four months, several residents and organizations in New Jersey --including New Jersey Policy Perspective and clients of a prominent law firm-- have filed records requests with the city to find about more about the bid.

Every one of them has been denied.

"With ... tax dollars on the line, the state and city of Newark have a responsibility to be as transparent as possible," said Jon Whiten, director of N.J. Policy Perspective, a left-leaning think tank. The organization filed a records request in January.

A few details of Newark's Amazon HQ2 bid process have slipped out since the deadline in October, including the fact that the city is offering $7 billion in tax credits in an attempt to attract the company.

That tax incentive package would dwarf the highest subsidy held by a company in New Jersey -- $390 million given to Ameream LLC and Meadow Amusement in 2013 to develop the retail and entertainment American Dream complex.

Nonetheless, specifics have been elusive, and at least one city -- Tacoma, Wash. -- has publicly disclosed that Amazon told the city to stay silent. People involved in the Louisville bid said they have a non-disclosure with the company. Kansas City and St. Louis claimed the same.

In January, Amazon held a call with Newark -- and told the city the remaining HQ2 process would be kept quiet, according to ROI-NJ, which broke the story.

Newark offered a different reason than other cities for in its record request denials:

It would give the city's competitors an edge, they said. Both Amazon and the organization that drafted the proposal for Newark could not be reached for comment.

"Other cities and towns in New Jersey have released their proposals," countered CJ Griffin, an attorney at Pashman Setin Walder, whose clients have filed requests with Newark asking for either the entire bid, or parts of it. All have been denied.

"We don't see why Newark would need to keep that information secret," she said, adding that her clients want to know how the bid was structured and what kind of financial deals, beyond the $7 billion in tax credits, it offered Amazon.

New Jersey Policy Perspective, an organization that focuses on tax incentives and subsidies, filed a request to see what kind of narrative the state was using to get Amazon to come to Newark.

"New Jersey leaders talked about how great Newark was for all these different reasons but then they are also saying that they are going to give seven billion in tax breaks to get Amazon her here," Whiten said. "We wanted to see the ranking - if they put the incentives as the main selling point or the other points about the city."

Griffin gained access to other New Jersey towns' proposal which were released to the public through record requests. Combined, those bids total close to 600 pages.

Now they are part of a lawsuit filed in Newark.

Griffin's client Steven Wronko is suing the city for access to the proposal.

Newark had previously denied his record requests for not only the proposal, but also for any contracts the city held with third-party vendors who helped prepare the bid.

Griffin said many of the agencies throughout the country that worked on the proposals, including those in New Jersey, hired writers and public relations companies to help promote the city and draft the bid.

Amazon identified 20 finalists for its HQ2 search in January, including New York City, Atlanta, Chicago and Nashville.

Boston, Philadelphia and Miami released their proposals to the public, Griffin said.

"Mr. Wronko wants to know how much money was spent in creating the proposal itself," she said.

Part of the reason why some cities throughout the U.S. have denied requests is because private institutions drafted the proposals and are not always subject to open record laws, Whiten said.

The Newark Community Economic Development Corporation (CEDC) drafted the city's proposal and describes itself as an "economic development catalyst" for the state.

It is technically independent but is also linked to the government, Whiten said.

"Some have been saying these agencies are just a defecto arm of city government," he said. "But we expected a denial from the get go."

Erin Banco may be reached at ebanco@njadvancemedia.com. Follow her on Twitter @ErinBanco. Find NJ.com on Facebook.

Update: ROI-NJ broke the story about the Amazon call with Newark, not GeekWire.