Feb 16 (Reuters) - A Starbucks labor group on Friday sent a letter to the U.S. Securities and Exchange Commission (SEC), calling on the company to disclose costs arising from anti-union campaigns, which the alliance estimates to be at least $240 million.

The coffee giant has faced nationwide campaign to unionize its stores, with workers walking out during a key promotional event in November in a strike organized by the Workers United union demanding improved staffing and schedules.

The Strategic Organizing Center (SOC), a coalition of North American labor unions, said Starbucks "needs to immediately provide full disclosure of the total costs and liabilities ... in order for ... informed voting decisions before the 2024 annual meeting."

The shareholder group said the costs include litigation, employee lost time, as well as liabilities associated with alleged labor law violations.

The U.S. Supreme Court last month agreed to hear Starbucks' appeal of a court ruling that required it to rehire seven employees at one of its cafes in Memphis, Tennessee who a federal agency determined were fired for supporting unionization.

The SOC had in November nominated three candidates to the board of Starbucks.

The annual meeting, when Starbucks shareholders will vote on the composition of its eight-member board, is scheduled for March 13.

Starbucks and the SEC did not immediately respond to Reuters' requests for comment. (Reporting by Savyata Mishra in Bengaluru; Editing by Maju Samuel)