The proposal won 52% of votes. Results came the same day ex-Chief Executive Howard Schultz testified before a U.S. Senate committee, defending the company against claims that it illegally fired pro-union employees, among other allegations.

"It is clear from the vote result in the proposal that our investors share our commitment to our partners," Starbucks said in its regulatory filing disclosing the results.

Starbucks reiterated that it is now "undertaking an independent, third-party human rights impact assessment, which will include a deeper-level review of the principles of freedom of association and the right to collective bargaining."

The Seattle-based company said it will use findings of the review to "understand how we can best support our partners."

(Reporting by Hilary Russ; Editing by Stephen Coates)

By Hilary Russ