BOSTON (Reuters) - BlackRock Inc BLK.N on Thursday called on securities regulators to set international standards for shareholder voting rights, suggesting they resolve one of the thorniest debates in corporate governance.

FILE PHOTO: The BlackRock logo is seen at the BlackRock Japan headquarters in Tokyo, Japan, October 20, 2016. REUTERS/Toru Hanai/File Photo

The world's largest asset manager made the call in a letter to index provider MSCI, which had sought comments about a proposal it is considering to adjust the index weighting of stocks like Facebook Inc FB.O and Google parent Alphabet Inc GOOGL.O to account for their unequal voting structures.

BlackRock, which manages $6.3 trillion, said while it appreciates the index provider’s attention to the issues, MSCI’s proposed changes could distort markets. Instead, “we believe that policymakers, not index providers, should set corporate governance standards,” it stated in the letter, signed by BlackRock Vice Chairman Barbara Novick and posted on the firm’s website.

Since last year a number of high-profile technology firms, including Spotify Technology SA SPOT.N, Dropbox Inc DBX.O and Snap Inc SNAP.N, have listed shares with a voting structure that gives lopsided decision-making power to insiders. According to the Council of Institutional Investors, among 124 IPOs in 2017, 23 had unequal voting rights, although some would give outside investors more voting power over time.

Corporate executives say the structures help their firms focus on long-term growth.

BlackRock and rivals like State Street Corp STT.N and Vanguard Group have criticized the trend but have bought the shares to fill index funds they say must try to replicate mandated market segments.

MSCI and other providers last year made changes that excluded some stocks with unequal rights, like Snap, from widely followed indexes, including the S&P 500 and the Russell 1000. MSCI said in January it might make further changes after more consultation with clients.

BlackRock’s Novick wrote that a global body like the International Organization of Securities Commissions would be well-positioned to suggest listing standards that national regulators could use. A Madrid-based spokeswoman for the organization said it has not undertaken work on the matter.

U.S. regulations are still under development. A committee that advises the U.S. Securities and Exchange Commission in March recommended reforms like clear disclosures of different voting rights and of the risks that could result.

SEC Chairman Jay Clayton said at the time he would like analysis of related areas like concerns about short-term investing and the attractiveness of U.S. capital markets. In February, Commissioner Robert Jackson said stock exchanges should develop some kind of limit on dual-class structures.