The New York Times reported last month a senior Wal-Mart lawyer received an email from a former executive at Walmex in 2005 describing how the Mexican affiliate had paid bribes to obtain permits to build stores in Mexico.

The newspaper also said senior Wal-Mart officials stymied an internal investigation into the alleged bribery, which involved suspect payments worth $24 million.

Wal-Mart has said it will cooperate with authorities looking into the allegations. It could not immediately be reached for further comment on Tuesday outside regular U.S. business hours.

Liu said the bribery allegations were damaging, but reports of a widespread cover-up, involving Wal-Mart's top executives, "could have even more devastating consequences."

"Time and again our pension funds have approached Wal-Mart's board with serious concerns about its practices in the U.S. and abroad and received only empty reassurances. This board has failed its shareholders," Liu said.

The pension funds, which represent only a tiny fraction of Wal-Mart's total equity, said they would vote against Chairman Robson Walton, Chief Executive Michael Duke, former CEO Lee Scott, current audit committee chairman Christopher Williams, and audit committee director Arne Sorenson at the company's annual shareholders meeting on June 1.

However, the funds said Walton's 49.5 percent ownership effectively guaranteed his re-election and that of his fellow directors.

The New York City Pension Funds consist of the New York City Employees' Retirement System, Teachers' Retirement System, New York City Police Pension Fund, New York City Fire Department Pension Fund and the Board of Education Retirement System.

(Reporting by Sakthi Prasad; Editing by Mark Potter)

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