Shareholder support for disclosure of corporate political support continues to build.

The Center for Political Accountability, examining results of disclosure proposals for the 2010 annual meeting season, found that shareholder support for disclosure rose to a record 30.25% at 28 meetings.

Since 2004, about 200 disclosure resolutions have been submitted on corporate proxies.

Disclosure support at four companies was particularly strong: Coventry Healthcare, 46%; Express Scripts, 42%; CVS Caremark, 41.35%; Sprint Nextel, 41.2%, and Allstate, 39.7%.

Bruce Freed, President of the CPA, says the results indicate that “more and more (investors) are calling for an end to the secrecy that has cloaked corporate political spending and want accountability.”

He added: “When you consider that the majority of votes side with management as a matter of course, the substantial support from retail and institutional shareholders shows the broad support for political disclosure.”

The Center recently launched an online database that allows users to examine how specific companies treat political accountability and disclosure.

Corporate political campaign support has become a hot button issue this year, particularly in view of the January 5-4 decision by the U.S. Supreme Court removing limits on corporate and union spending on political ads.

Critics of the decision fear a deluge of corporate spending, prompting Democrats to seek to limit the decision and to require contributors to disclose their identities.  The legislation, labeled the DISCLOSE Act, passed the House 219 to 206 in late June, but backers had to make key concessions to achieve passage.  One change would exempt the National Rifle Association from the bill’s disclosure requirements. And opponents, led by the U.S. Çhamber of Commerce, have labeled the measure an assault on free speech.

Similar legislation introduced in the U.S. Senate faces an uncertain future, particularly in an election year.

The Center for Political Accountability, the Council of Institutional Investors and a number of shareholder advocacy groups have launched a letter-writing campaign urging companies in  the Standard & Poor’s 500 Index  to disclose all political contributions they make with corporate funds.

Currently, 73 S&P 500 companies, including Hewlett-Packard, Merck, United Technologies, eBay, Aetna and Microsoft, make such disclosures, they said.

The letter campaign was prompted by the  U.S. Supreme Court’s Jan. 21 ruling in Citizens United v. Federal Election Commission,  which now permits corporations, labor unions and other groups to make independent contributions during political campaigns.

Reaction to the decision has reached multi-decibel levels with supporters praising its free speech position and opponents predicting massive corporate efforts to influence political campaigns.

The letter to S&P Index companies declares that the ruling “is likely to put companies under immense pressure to use shareholder funds to support candidates, groups and causes whose positions and activities could threaten a company’s reputation, bottom line and shareholder value.”

Disclosure will help companies “protect themselves from the pressure to give and from ill-considered political spending,” said Bruce Freed, President of the Center for Political Accountability.

Ann Yerger, executive director of the Council of Institutional Investors, which promotes good corporate governance, said “investors need to know how their money is being spent in the political arena. And boards need to step up to the plate and ensure that political checks the company writes enhance, not erode, shareholder value.”

The Council called on corporate boards to “monitor, assess and approve all company political contributions, and to develop and disclose publicly, on an annual basis, the amounts and recipients of all monetary and non-monetary contributions.”