Major corporations are increasingly saying that discrimination based on sexual orientation will not be tolerated in the workplace.

According to a new report out from LGBT civil rights organization Equality Forum, 471 (94.2 percent) of the 2008 list of Fortune 500 companies voluntarily include sexual orientation in their employment nondiscrimination policies.

“The Fortune 500 have overwhelmingly decided that including sexual orientation is in the best corporate interest and helps communicate corporate values to the estimated $660 billion annual domestic GLBT consumer market,” says Malcolm Lazin, Executive Director of Equality Forum.

The latest results suggest a marked increase in the number of companies embracing sexual orientation nondiscrimination policies since Equality Forum began contacting Fortune 500 companies five years ago. In fall 2003, just 323 (64.6 percent) companies explicitly provided sexual orientation protection in their workplace policies. However by fall 2004, after Equality Forum reached out to the CEOs, Human Resource Directors and all members of the Boards of Directors of the 177 companies without such protections, 405 (81 percent) Fortune 500 companies opted to include sexual orientation in their workplace nondiscrimination policies.

Notable among the Fortune 500 companies that do not specifically provide sexual orientation protection is Exxon Mobil, the largest such corporate interest on the list. Other noncompliant companies include DISH Network, Virgin Media and GMAC.

Changing corporate attitudes appear to be mirroring those of the general public according to Gallup’s May 2008 Values and Beliefs Poll, which found that 89 percent of U.S. citizens believe gays and lesbians should have equal rights in job opportunities.

While there is currently no federal workplace protection based on sexual orientation, some twenty states include sexual orientation nondiscrimination in their workplace statutes.