Lobbyists representing leading companies in the Silicon Valley and Hollywood have placed tremendous pressure to defeat legislation designed to shine a spotlight onto wage disparities by gender at California companies.

Gov. Jerry Brown is currently deciding the fate of AB 1209, a bill passed by both chambers of the legislature that requires large firms with 500 or more employees in the state to file reports with the secretary of state detailing the gender pay gap for people working in the same position.

Brown has until Sunday to sign or veto the legislation. If he takes no action, the bill becomes law without his signature.

What companies are pressing Brown to kill the bill? It’s a Sacramento mystery.

A number of business trade associations, including the Motion Picture Association of America, TechNet, and Computing Technology Industry Association, have been lobbying the governor. Those three groups represent the largest movie production studios and technology firms in the state, but when advocating on issues of public policy, they are not required to disclose the firms for whom they are lobbying.

The groups did not respond to requests for comment regarding which member companies asked them to push against AB 1209.

The trio last month signed a letter claiming that the proposal would create an unfair image of employers by failing to take into account jobs that are based on commission, where pay differentials may account for performance rather than any form of gender discrimination. They have urged elected officials to oppose the legislation.

“Public display of the data adds insult to injury. Employers would be required to provide statistics on job duties, wages and gender, but without the factors such as experience and seniority that the law says are legitimate reasons for wage gaps,” Kara Bush of CompTIA wrote in a column co-authored with the California Chamber of Commerce, denouncing the bill.

At the Assembly hearing to discuss the bill, another CompTIA lobbyist, Chris McHill, testified in opposition, claiming that AB 1209 would simply create new “avenues for enterprising plaintiffs lawyers to go and sue those individual companies.”

Members of CompTIA include Google, Apple, Ingram Micro, and other companies that may be forced to report gender pay data under the law.

Lobbying disclosures show that Google, which has faced mounting questions over its own gender pay gap, lobbied on the legislation, although it is not clear what position the technology giant took. Google’s primary Sacramento lobbying firm, KP Public Affairs, engaged on AB 1209 sometime between April and June, as the bill made its way through committee, according to the disclosures.

Asked by The Intercept if Google supports or opposes the legislation, a company spokesperson declined to answer. He later contacted us to say that Google “never instructed any firms to lobby on this to the legislature, governor or anywhere else.” KP Public Affairs, the spokesperson added, “[was] at meetings where it was discussed, among other topics, so we disclosed it.”

Google has many reasons to be wary of further scrutiny over its compensation practices.

The firm waged a legal battle against the Department of Labor over an audit designed to determine whether the company complied with equal pay laws.

In September, the New York Times obtained a spreadsheet from Google that contained salary and bonus information. While the data do not provide a full view of Google salaries, the spreadsheet appears to show that women are paid less than men for the same entry level and mid-level positions.

Also last month, three former Google employees filed a class-action lawsuit, alleging that the firm engaged in widespread gender discrimination.

James Finberg, the attorney representing the plaintiffs in the suit, said he wouldn’t be surprised if firms like Google are lobbying against pay gap transparency efforts. Finberg noted that the Department of Labor audit already found statistically significant pay disparities for women across the board. “So to the extent that that’s reported publicly, it’s embarrassing for Google,” he said.

Top photo: The Google logo is seen at the Google headquarters in Mountain View, Calif. on Sept. 2, 2011.