The Syosset developer working on a retail and entertainment complex that is a key part of the Nassau Coliseum overhaul has sued Forest City Ratner Cos., arguing that the company, which plans to begin redeveloping the arena this summer, has tried to "usurp sole control of the project."

Blumenfeld Development Group filed a lawsuit Tuesday in state Supreme Court in Mineola seeking to enforce a "joint venture partnership" with Forest City Ratner. The suit seeks an injunction preventing Ratner from moving ahead with the development without Blumenfeld, and seeks unspecified monetary damages.

The suit came four days after Forest City Ratner filed suit against Blumenfeld, asking the court to declare that the firms are not partners. In its 45-page complaint, Blumenfeld contends the companies have been partners for 18 months and Ratner "engaged in an unlawful and deceitful campaign to manufacture a series of false and misleading accusations against BDG."

"Forest City has chosen to jeopardize the project by refusing to resolve matters, then filing an ill-conceived, frivolous lawsuit," said Blumenfeld attorney Ronald Rosenberg. "We are confident . . . the Forest City Companies will be held fully accountable for their misconduct."

Forest City spokeswoman Ashley Cotton said "our concern is the long-term economic viability of a project that we believe meets the needs and expectations of the county. Unfortunately, their vision was at odds with ours."

Blumenfeld's plan includes about 300,000 square feet of retail and restaurant space, while Forest City wants a 188,000-square-foot entertainment complex.

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The Blumenfeld suit contends the company is 50 percent partners with Forest City on the complex and in any future redevelopment of the Coliseum site. Blumenfeld also says it has an option to purchase five percent of the arena property. Cotton said "there was never a final partnership agreement."

Rosenberg said it was unclear whether the dueling suits will delay the retail and entertainment complex, but conceded it "does not aid in the project."

Brian Nevin, spokesman for County Executive Edward Mangano, declined to comment on the lawsuits but said "the administration has been assured that such disputes will not delay" the Coliseum renovations.

Forest City officials said a memorandum of understanding, which was signed in August and expired in November, is the only formal agreement between the firms.

But in its suit, Blumenfeld details public statements and private emails in which Forest City executive chairman Bruce Ratner referred to himself and company chief executive Ed Blumenfeld as "partners." The suit cites language in Nassau's 2013 lease agreement with Ratner in which BDG is listed as a member of Nassau Events Center, the Forest City affiliate created for the project.

Blumenfeld and Forest City were among four companies that bid on the redevelopment of the Coliseum and its surrounding property in 2013. After Nassau settled on Forest City and the Madison Square Garden Company as finalists, Blumenfeld signed on to Ratner's proposal agreeing to develop the retail and restaurant components. Rosenberg said the first signs of discord between the two firms occurred in November when Ratner attempted to bring a Memorial Sloan Kettering cancer treatment center to the redevelopment site. Ratner sits on Sloan Kettering's board of directors.

Blumenfeld officials said they raised concerns that the cancer center would displace about 1,000 parking spots. The suit claims Ratner became "enraged" when Blumenfeld raised the issue, and canceled weekly meetings with the firm and told BDG to stop communicating with the project's consultants and potential tenants.

Ratner's suit claims Blumenfeld took an "overly aggressive posture" against the Sloan Kettering project and nearly scuttled the deal.

Sloan announced plans in March to spend $140 million to build an outpatient treatment and research facility adjacent to the Coliseum.