WASHINGTON (Reuters) - Six U.S. senators on Wednesday introduced a bill that would require the U.S. securities watchdog to directly regulate firms such as Glass, Lewis & Co and Institutional Shareholder Services, which advise investors on how to vote in corporate elections.

The seal of the U.S. Securities and Exchange Commission hangs on the wall at SEC headquarters in Washington, June 24, 2011. REUTERS/Jonathan Ernst

The bipartisan bill comes as corporate lobbyists, including the U.S. Chamber of Commerce and the National Association of Manufacturers, are campaigning to rein-in “proxy advisers,” which they say have too much sway over corporate democracy.

The role of proxy advisers is part of a broader debate over how to improve governance at U.S. companies, which since the financial crisis have faced growing pressure from investors to consider issues like climate change and employee diversity.

Proxy advisers often support shareholder proposals on these issues, bringing them into conflict with company management views that the firms are effectively hijacking the boardroom. They say proxy advisers should be regulated in a manner similar to rating agencies.

In particular, they complain that the firms are potentially conflicted because ISS offers consulting services to the same companies on which it provides voting recommendations, while Glass Lewis is largely owned by an activist investor, the Ontario Teachers’ Pension Plan.

The Corporate Governance Fairness Act bill would require the U.S. Securities and Exchange Commission to regulate proxy advisers directly under the Investment Advisers Act. This would make the firms subject to periodic SEC examinations, which would include a serious review of the firms’ conflicts of interest policies.

The SEC and Glass Lewis did not immediately respond to requests for comment.

A spokesman for ISS said the company continues to believe additional federal legislation is not necessary.

“If this bill were to pass ... ISS will do what we always have done: we will comply in full with the law and with the highest standards of the proxy advisory industry,” he said in an email statement.

The bill is sponsored by Democratic Senators Jack Reed, Doug Jones and Heidi Heitkamp, and Republican Senators David Perdue, Thom Tillis and John Kennedy and has been endorsed by the Consumer Federation of America, the New York Stock Exchange and the Society for Corporate Governance.

While it is unlikely to become law in this Congress, the bill will add to growing pressure on the SEC, which on Thursday is holding a closely watched roundtable to discuss the proxy process, including tighter scrutiny of advisers.