Darden Restaurants Inc. and its two activist investors sparred this week in competing federal filings and letters as they dug in their positions in the unfolding battle over board seats.

All 12 of Orlando, Fla.-based Darden’s board seats are up for election at the approaching Sept. 30 annual shareholder meeting, with investor Starboard Value L.P. putting forth a full slate of directors and Darden offering the activist three seats.

In the wake of the July 28 sale of 706-unit Red Lobster to Golden Gate Capital, the announcement that Clarence Otis, Jr., would be leaving and the company’s decision to split Otis chairman and chief executive roles, Darden filed Monday a presentation with the Securities and Exchange Commission and an open letter to shareholders “to correct a number of inaccurate and misleading statements.”

Activist investors Starboard Value L.P., which now holds about 8.8 percent of Darden shares, countered Tuesday with its own SEC filing, wherein Jeffrey C. Smith, Starboard’s chief executive, said, “Unfortunately, Darden continues to get many things wrong.”

Fellow activist investor Barington Companies Equity Partners L.P. on Tuesday sent an open letter to Darden urging adoption of Starboard’s slate.

“We believe it is abundantly clear that a change in the board provides all shareholders with the best opportunity to own a stronger and better performing company,” Smith said.

Part of the argument returned to the sale of Red Lobster.

On Monday, Darden said its “board determined that divesting Red Lobster was in the best interests of Darden and its shareholders.  Despite numerous actions taken to improve the business, Red Lobster experienced years of declines in guest traffic, resulting in volatile and consistently weakening financial performance that significantly burdened Darden's results.  Red Lobster's negative trends were continuing and accelerating at the time its sale was announced in May.”

Darden also disputed Starboard’s claims that Red Lobster was sold at a discount.

“The $2.1 billion purchase price represents a premium multiple compared to comparable restaurant deals and exceeded many industry analysts' expected valuation ranges for the business,” Darden noted in response, “particularly taking into account Red Lobster's deteriorating performance.”

On Tuesday, Smith cited “the board's arguments for why they needed to give away Red Lobster instead of listening to their shareholders…. Since they were concerned that they couldn't improve Red Lobster, it was easier for them to just give it away. To that we would say, why should we trust them to turn around Olive Garden?”

Smith said Starboard would publish a “transformation plan for Darden” in September.

“This plan involves company-wide operational improvements and a turnaround of Olive Garden, along with strategic initiatives including a value-enhancing strategy for Darden's real estate assets, a potential spin-off of the company's Specialty Restaurant Group, and a value-enhancing franchising strategy,” Smith said.

“In order to implement this plan, however, it is essential that Darden establish strong leadership at the CEO and board level — leadership with relevant experience, a proven ability to drive results, and a strong commitment to, and respect for, proper corporate governance,” Smith said in his SEC filing.