“Mr. Demoulas’ authoritarian regime” is one way Market Basket’s board of directors describes recently ousted CEO Arthur T. Demoulas’ management of the Tewksbury-based grocery store chain in a new lawsuit.

The board’s four-word description encapsulates much of its reasoning for placing Demoulas on paid leave back in May and then unanimously voting to fire him during a board meeting Tuesday night.

“Mr. Demoulas forced the Board to choose between accepting his autocratic control of Market Basket or terminating him in order to protect a vibrant and growing business that cannot flourish over the long-term under the leadership of a dictator,” the lawsuit reads.

The board’s decision marked the second time in less than 15 years that Demoulas has been removed from his position at Market Baske

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